-- If problem is still gone, then cause is a program loaded during windows startup.  Possibilities include: antivirus SW, virus/malware, background downloads such as program updates
   -- If problem is NOT gone, then cause is likely a Thunderbird addon - eliminate them by disabling each one at a time in Tools | addons | extensions and restarting

My previous posting was to the wrong topic. Sorry. FOr this topic, Start *Windows'* safe mode with networking enabled - win8 http://windows.microsoft.com/en-us/windows-8/windows-startup-settings-safe-mode - win7 http://windows.microsoft.com/en-us/windows/start-computer-safe-mode#start-computer-safe-mode=windows-7 - XP http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/boot_failsafe.mspx Still In Windows safe mode, start thunderbird in safe mode - http://support.mozillamessaging.com/en-US/kb/safe-mode Does problem go away? - If no, then problem is either: bug in Thunderbird, in your Thunderbird profile, your mail provider. Please post into topic the contents of Help | Troubleshooting | copy text to clipboard - If yes, (still in Windows safe mode) ... start Thunderbird normally -- If problem is still gone, then cause is a program loaded during windows startup. Possibilities include: antivirus SW, virus/malware, background downloads such as program updates -- If problem is NOT gone, then cause is likely a Thunderbird addon - eliminate them by disabling each one at a time in Tools | addons | extensions and restarting