re :the main account seems to be frozen, I can't receive new emails from it and sending email out from it is very very slow.

If you logon to webmail account using a browser, are there new emails that have not downloaded? Are there no recent emails? If webmail is not getting new emails then it is possible you have reached your quota and server cannot receive more until emails are deleted.

Confirm new emails are being received on server.

Do you compact your folders especially Inbox on a regular basis? Compacting fully removes all hidden marked as deleted emails and reduces the file size.

Are you talking about a Pop or Imap mail account?

The email account is through gmail but it's for a business. Yes, when I log into the web based portal there are new messages there. This is how I know the new messages aren't getting through on Thunderbird. I compact the folders every time it asks me if I want to compact them too. The only thing I've found that helps (for a little while) is completely closing down my computer then starting it back up and opening Thunderbird again. Then it clears out everything again but shortly after this it freezes again. Just closing Thunderbird and opening it up again doesn't clear things out. I have to close the whole computer out and retart to get things cleared up again.

Please perform a test: Restart Computer in 'Safe Mode with Networking' mode. Start Thunderbird.

Stay in that computer mode as you need to ascertain if the freezing also occurs in 'Safe Mode with Networking' mode. Please report back on results.

I actually just updated Thunderbird with the newest edition, then ran CCleaner which goes in and cleans out all the cache and temp files of Thunderbird. Restarted my computer and (knock on wood) so far it all seems to be working correctly now.