how to fix RETR Command blockage

Have been useing a tiscali email address for several years. Three weeks ago a RETR Command created a blockage and I could no longer download emails. There must be hundreds backed up behind the blockage.It seems to be a common problem but nothing I have read helps. Full message as follows: The RETR Command did not succeed, error retrieving message, mail server pop3.tiscali.co.uk responded, cannot open file/nfs2mailgb/mail_06/03/23 mddgordon%tiscali.co.uk/oa70003c58807563.msg emo2 file does not exist. Would it help to uninstall and reinstall Thunderbird, and would I loose all existing emails, and saved emails in folders?.