*Restart the operating system in '''[http://en.wikipedia.org/wiki/Safe_mode safe mode with Networking]'''. This loads only the very basics needed to start your computer while enabling an Internet connection. Click on your operating system for instructions on how to start in safe mode: [http://windows.microsoft.com/en-us/windows-8/windows-startup-settings-including-safe-mode Windows 8], [http://windows.microsoft.com/en-us/windows/start-computer-safe-mode#start-computer-safe-mode=windows-7 Windows 7], [http://windows.microsoft.com/en-us/windows/start-computer-safe-mode#start-computer-safe-mode=windows-vista Windows Vista], [http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/boot_failsafe.mspx?mfr=true" Windows XP], [http://support.apple.com/kb/ht1564 OSX] ; If safe mode for the operating system fixes the issue, there's other software in your computer that's causing problems. Possibilities include but not limited to: AV scanning, virus/malware, background downloads such as program updates.

Thanks. I figured it out without having to do ALL of that!!! :) My Free Avast Antivirus ended a few days ago, and I had to register and install a new one. I didn´t check the Sheild Settings which were on for my Thunderbird email. I had this problem before. Thunderbird doesn´t work if the Avast Email Shield is on. I don´t know why, so I always unchecked it. When I installed the new Avast, ALL of the Shields were checked, and that was the problem. The minute you said AV, I realized what the problem was. :) Thank you. Have a great day. Dicarlo