Ciao, da stamane appena clicco sull'icona di outlook express immediatamente il pc si disconnette da internet, ho provato almeno una dozzina di volte, sempre lo stesso
posto il log di hijack, non si sa mai:

Logfile of Trend Micro HijackThis v2.0.2
Scan saved at 15.40.22, on 05/12/2009
Platform: Windows XP SP2 (WinNT 5.01.2600)
MSIE: Internet Explorer v7.00 (7.00.6000.16915)
Boot mode: Normal

Running processes:
C:\WINDOWS\System32\smss.exe
C:\WINDOWS\system32\winlogon.exe
C:\WINDOWS\system32\services.exe
C:\WINDOWS\system32\lsass.exe
C:\WINDOWS\system32\svchost.exe
C:\Programmi\Windows Defender\MsMpEng.exe
C:\WINDOWS\System32\svchost.exe
C:\WINDOWS\system32\spoolsv.exe
C:\WINDOWS\Explorer.EXE
C:\Programmi\Google\Update\1.2.183.13\GoogleCrashHandler.exe
C:\PROGRA~1\AVG\AVG8\avgwdsvc.exe
C:\WINDOWS\system32\cisvc.exe
C:\Programmi\File comuni\Microsoft Shared\VS7DEBUG\MDM.EXE
C:\Programmi\PC Tools Firewall Plus\FWService.exe
C:\PROGRA~1\AVG\AVG8\avgrsx.exe
C:\PROGRA~1\AVG\AVG8\avgnsx.exe
C:\Programmi\CyberLink\Shared files\RichVideo.exe
C:\PROGRA~1\AVG\AVG8\avgtray.exe
C:\Programmi\PC Tools Firewall Plus\FirewallGUI.exe
C:\Programmi\Google\Quick Search Box\GoogleQuickSearchBox.exe
C:\Programmi\Google\GoogleToolbarNotifier\GoogleToolbarNotifier.exe
C:\WINDOWS\system32\ctfmon.exe
C:\WINDOWS\system32\wuauclt.exe
C:\Programmi\Digisoft AntiDialer\AntiDialer.exe
C:\WINDOWS\system32\msfeedssync.exe
C:\Programmi\Digisoft AntiDialer\AntiDialer.exe
C:\WINDOWS\system32\cidaemon.exe
C:\Programmi\Internet Explorer\iexplore.exe
C:\Programmi\DALLA RETE\hijackthis\HijackThis.exe

R0 - HKCU\Software\Microsoft\Internet Explorer\Main,Start Page = http://www.libero.it/
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Default_Page_URL = http://go.microsoft.com/fwlink/?LinkId=69157
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Default_Search_URL = http://go.microsoft.com/fwlink/?LinkId=54896
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,SearchAssistant = http://www.crawler.com/search/ie.aspx?tb_id=60327
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,CustomizeSearch = http://dnl.crawler.com/support/sa_customize.aspx?TbId=60327
R1 - HKLM\Software\Microsoft\Internet Explorer\Main,Search Page = http://go.microsoft.com/fwlink/?LinkId=54896
R0 - HKLM\Software\Microsoft\Internet Explorer\Main,Start Page = http://go.microsoft.com/fwlink/?LinkId=69157
R0 - HKLM\Software\Microsoft\Internet Explorer\Search,SearchAssistant = http://www.crawler.com/search/ie.aspx?tb_id=60327
R0 - HKLM\Software\Microsoft\Internet Explorer\Search,CustomizeSearch = http://dnl.crawler.com/support/sa_customize.aspx?TbId=60327
R0 - HKCU\Software\Microsoft\Internet Explorer\Main,Local Page =
R0 - HKLM\Software\Microsoft\Internet Explorer\Main,Local Page =
R0 - HKCU\Software\Microsoft\Internet Explorer\Toolbar,LinksFolderName = Collegamenti
R3 - URLSearchHook: AVG Security Toolbar BHO - {A3BC75A2-1F87-4686-AA43-5347D756017C} - C:\Programmi\AVG\AVG8\Toolbar\IEToolbar.dll
R3 - URLSearchHook: (no name) - *{CFBFAE00-17A6-11D0-99CB-00C04FD64497} - (no file)
O2 - BHO: Supporto di collegamento per Adobe PDF Reader - {06849E9F-C8D7-4D59-B87D-784B7D6BE0B3} - C:\Programmi\File comuni\Adobe\Acrobat\ActiveX\AcroIEHelper.dll
O2 - BHO: WormRadar.com IESiteBlocker.NavFilter - {3CA2F312-6F6E-4B53-A66E-4E65E497C8C0} - C:\Programmi\AVG\AVG8\avgssie.dll
O2 - BHO: Spybot-S&D IE Protection - {53707962-6F74-2D53-2644-206D7942484F} - C:\PROGRA~1\SPYBOT~1\SDHelper.dll
O2 - BHO: SSVHelper Class - {761497BB-D6F0-462C-B6EB-D4DAF1D92D43} - C:\Programmi\Java\jre1.6.0_07\bin\ssv.dll
O2 - BHO: AVG Security Toolbar BHO - {A3BC75A2-1F87-4686-AA43-5347D756017C} - C:\Programmi\AVG\AVG8\Toolbar\IEToolbar.dll
O2 - BHO: Google Toolbar Helper - {AA58ED58-01DD-4d91-8333-CF10577473F7} - C:\Programmi\Google\Google Toolbar\GoogleToolbar_32.dll
O2 - BHO: Google Toolbar Notifier BHO - {AF69DE43-7D58-4638-B6FA-CE66B5AD205D} - C:\Programmi\Google\GoogleToolbarNotifier\5.4.4525.1752\swg.dll
O2 - BHO: Google Gears Helper - {E0FEFE40-FBF9-42AE-BA58-794CA7E3FB53} - C:\Programmi\Google\Google Gears\Internet Explorer\0.5.32.0\gears.dll
O3 - Toolbar: AVG Security Toolbar - {CCC7A320-B3CA-4199-B1A6-9F516DD69829} - C:\Programmi\AVG\AVG8\Toolbar\IEToolbar.dll
O3 - Toolbar: Google Toolbar - {2318C2B1-4965-11d4-9B18-009027A5CD4F} - C:\Programmi\Google\Google Toolbar\GoogleToolbar_32.dll
O4 - HKLM\..\Run: [AVG8_TRAY] C:\PROGRA~1\AVG\AVG8\avgtray.exe
O4 - HKLM\..\Run: [00PCTFW] "C:\Programmi\PC Tools Firewall Plus\FirewallGUI.exe" -s
O4 - HKLM\..\Run: [MSConfig] C:\WINDOWS\PCHealth\HelpCtr\Binaries\MSConfig.exe /auto
O4 - HKLM\..\Run: [Google Quick Search Box] "C:\Programmi\Google\Quick Search Box\GoogleQuickSearchBox.exe" /autorun
O4 - HKCU\..\Run: [swg] "C:\Programmi\Google\GoogleToolbarNotifier\GoogleToolbarNotifier.exe"
O4 - HKCU\..\Run: [ctfmon.exe] C:\WINDOWS\system32\ctfmon.exe
O4 - HKUS\S-1-5-19\..\Run: [CTFMON.EXE] C:\WINDOWS\system32\CTFMON.EXE (User 'SERVIZIO LOCALE')
O4 - HKUS\S-1-5-20\..\Run: [CTFMON.EXE] C:\WINDOWS\system32\CTFMON.EXE (User 'SERVIZIO DI RETE')
O4 - HKUS\S-1-5-18\..\Run: [CTFMON.EXE] C:\WINDOWS\system32\CTFMON.EXE (User 'SYSTEM')
O4 - HKUS\.DEFAULT\..\Run: [CTFMON.EXE] C:\WINDOWS\system32\CTFMON.EXE (User 'Default user')
O4 - Global Startup: Digisoft AntiDialer.lnk = C:\Programmi\Digisoft AntiDialer\AntiDialer.exe
O6 - HKCU\Software\Policies\Microsoft\Internet Explorer\Control Panel present
O6 - HKLM\Software\Policies\Microsoft\Internet Explorer\Control Panel present
O8 - Extra context menu item: E&sporta in Microsoft Excel - res://C:\PROGRA~1\MICROS~2\OFFICE11\EXCEL.EXE/3000
O8 - Extra context menu item: Google Sidewiki... - res://C:\Programmi\Google\Google Toolbar\Component\GoogleToolbarDynamic_mui_en_60D6097707281E79.dll/cmsidewiki.html
O9 - Extra button: (no name) - {08B0E5C0-4FCB-11CF-AAA5-00401C608501} - C:\Programmi\Java\jre1.6.0_07\bin\ssv.dll
O9 - Extra 'Tools' menuitem: Sun Java Console - {08B0E5C0-4FCB-11CF-AAA5-00401C608501} - C:\Programmi\Java\jre1.6.0_07\bin\ssv.dll
O9 - Extra button: (no name) - {09C04DA7-5B76-4EBC-BBEE-B25EAC5965F5} - C:\Programmi\Google\Google Gears\Internet Explorer\0.5.32.0\gears.dll
O9 - Extra 'Tools' menuitem: &Impostazioni di Google Gears - {09C04DA7-5B76-4EBC-BBEE-B25EAC5965F5} - C:\Programmi\Google\Google Gears\Internet Explorer\0.5.32.0\gears.dll
O9 - Extra button: Ricerche - {92780B25-18CC-41C8-B9BE-3C9C571A8263} - C:\PROGRA~1\MICROS~2\OFFICE11\REFIEBAR.DLL
O9 - Extra button: (no name) - {DFB852A3-47F8-48C4-A200-58CAB36FD2A2} - C:\PROGRA~1\SPYBOT~1\SDHelper.dll
O9 - Extra 'Tools' menuitem: Spybot - Search & Destroy Configuration - {DFB852A3-47F8-48C4-A200-58CAB36FD2A2} - C:\PROGRA~1\SPYBOT~1\SDHelper.dll
O9 - Extra button: Messenger - {FB5F1910-F110-11d2-BB9E-00C04F795683} - C:\Programmi\Messenger\msmsgs.exe
O9 - Extra 'Tools' menuitem: Windows Messenger - {FB5F1910-F110-11d2-BB9E-00C04F795683} - C:\Programmi\Messenger\msmsgs.exe
O16 - DPF: {D27CDB6E-AE6D-11CF-96B8-444553540000} (Shockwave Flash Object) - http://fpdownload2.macromedia.com/get/shockwave/cabs/flash/swflash.cab
O18 - Protocol: linkscanner - {F274614C-63F8-47D5-A4D1-FBDDE494F8D1} - C:\Programmi\AVG\AVG8\avgpp.dll
O20 - Winlogon Notify: avgrsstarter - C:\WINDOWS\SYSTEM32\avgrsstx.dll
O23 - Service: AVG Free8 WatchDog (avg8wd) - AVG Technologies CZ, s.r.o. - C:\PROGRA~1\AVG\AVG8\avgwdsvc.exe
O23 - Service: Google Update Service (gupdate) (gupdate) - Google Inc. - C:\Programmi\Google\Update\GoogleUpdate.exe
O23 - Service: Google Software Updater (gusvc) - Google - C:\Programmi\Google\Common\Google Updater\GoogleUpdaterService.exe
O23 - Service: InstallDriver Table Manager (IDriverT) - Macrovision Corporation - C:\Programmi\File comuni\InstallShield\Driver\11\Intel 32\IDriverT.exe
O23 - Service: PC Tools Firewall Plus (PCToolsFirewallPlus) - PC Tools - C:\Programmi\PC Tools Firewall Plus\FWService.exe
O23 - Service: Cyberlink RichVideo Service(CRVS) (RichVideo) - Unknown owner - C:\Programmi\CyberLink\Shared files\RichVideo.exe
O23 - Service: ServiceLayer - Nokia. - C:\Programmi\PC Connectivity Solution\ServiceLayer.exe
O23 - Service: Windows Live Setup Service (WLSetupSvc) - Unknown owner - C:\Programmi\Windows Live\installer\WLSetupSvc.exe (file missing)

--
End of file - 8165 bytes

EDIT; RISOLTO, bastava togliere la spunta in disconnetti dopo l'invio/ricezione dei messaggi in STRUMENTI/OPZIONI/CONNESSIONE. non so' come e' apparsa questa spunta.

grazie cmq

non mi sembra di vedere infezioni nel log, pero' ti consiglierei di spostarlo nella sezione sicurezza dove hai maggiore visibilita', fai una scansione con il malwarebytes, lo scaichi da aiutamici oppure da www.malwarebytes.org.