Try a Repair Folder from the folder right-click menu, Properties.

sfhowes said

Try a Repair Folder from the folder right-click menu, Properties.

This solves the problem temporarily , this problem happens several times in two weeks

This solves the problem temporarily , this problem happens several times in two weeks, is there any permanent solution to this problem, i am using an imap account

You could try rebuilding the Inbox by deleting the mbox and msf files from the profile folder, restarting TB and having it create a new folder, which would then sync with the IMAP server:

http://kb.mozillazine.org/Compacting_folders#Real_fix

Also, make sure the profile folder is excluded from antivirus scanning, to prevent corruption of the mail folders.