Try to delete the file popstate.dat in your profile. http://kb.mozillazine.org/Popstate.dat#Deleting_popstate.dat The article also explains where to find popstate.dat.

I deleted the popstate.dat for the account in question, hit 'get messages' and watched 2000+ messages ready to download. Around 1700 actually did download, but it failed in exactly the same spot as before.

Any other ideas to get past that and get the 324 other messages that are waiting?

Login to your account via webmail and delete the message causing the trouble.

According to yahoo (who manages my mail) I cannot log in via webmail as this account is POP. I'm trying to get them to delete the offending email, but it's not looking good. My email queue is at 900+ and growing.

According to yahoo I cannot log in via webmail

I doubt that. Try https://mail.yahoo.com

I gave up and went back to your original suggestion. I edited the popstate file and added a delete record for the msg that I kept getting over and over. The format was d longassid 0 The single 0 for the timestamp is what I didn't know before. When I polled again, the record was deleted and the rest of my new messages downloaded.

Thanks again for your help. Without it, I would still be scratching my head.

Excellent, you fixed your problem. Can you just mark the thread as 'Solved' please? Thank you.