What is your anti-virus software?

I use Avast.

Don't let Avast scan your Thunderbird profile folder, create an exception for the profile folder in Avast. http://kb.mozillazine.org/Profile_folder_-_Thunderbird

Don't let Avast scan incoming and outgoing messages. Don't let it scan attachments. And don't let it intercept your secure connection to the server.

Also see https://wiki.mozilla.org/Thunderbird:Testing:Antivirus_Related_Performance_Issues#AVAST

I tried to implement the things regarding Avast, but Thunderbird still freezes.

Try to start *Windows* in safe mode with networking enabled. - Win7 http://windows.microsoft.com/en-US/windows7/Start-your-computer-in-safe-mode

Still in Windows safe mode, start Thunderbird in safe mode. - https://support.mozilla.org/en-US/kb/safe-mode

Does the problem go away?

Something very strange just happened....

I started Thunderbird (as I have started it so many times before in the recent past), and all of a sudden it does not hang?

I have now been working on it for a few hours and it does not freeze. Very strange.

In the past day I have been using MS Outlook as my mail programme aiming at the same IMAP account. Outlook did not freeze.

Maybe I have (inadvertently) been resolving an issue with the mail folders or similar - Who knows......

It feels good that Thunderbird is up and running. However it does not feel so good that I don't know what caused the problems and if they will be back.

Thanks for all the help.

i have my thunderbird updated to 38.7.0 and after that my thunderbird goes no responding. when i start it it freezes and does that every few min. it was great till i updated to 38.7.0 please help me. i am using windows 8.1 and have avast