Email auto-downloading years of emails!!? advice?

[anticowboyism]

Since Jan. 1st I've been having this problem and it has turned my phone worthless. Any help or insight would be greatly appreciated.

I have a yahoo imap account setup on my diamond. I have it set to download and store the past 7 days worth of emails only. This setup has worked fine the entire year I've owned this phone, until now.

All of a sudden, on January 1st, the phone attempts to download all 10,000 emails from my yahoo account. By the time I noticed, it had got to about 4000 and completely crashed. It took hours to delete the account from the phone because as soon as it started up, it was bogged down by low memory, and still trying to download emails. This was on the stock sprint rom.

Fed up, I flashed to the latest Mystery rom. Got it all setup and fixed various issues it had. Last night it started to do the same thing. The phone crashed again this morning with close to 4000 emails (this time on the storage card, but it bogged down to a crawl nonetheless). I hard reset and have been restoring the phone today.

Any clues to what is causing this behavior? When it happens, my phone is pretty much useless for the next 12 hours while I fix everything. It seems probably a yahoo error, since all my phone settings are (and have always been) the same, 7 days maximum of emails stored.