Yahoo Mail Repeatedly Crashes Mozilla

My Mozilla is crashing constantly with Yahoo Mail. I'm using the "classic" version of Yahoo - but it has the messenger embedded in it. I've checked to "disable" messenger - but I don't find the file to do so (npYState.dll). Sometimes I can get online and work for 20-30 minutes - at other times, everything crashes the minute Yahoo mail fully loads. Though I've noticed this problem on and off for a number of weeks, the last 4-5 days have been the WORST when I can be blocked from my email for hours.

I rarely crash when on other websites - only Yahoo mail. This is frustrating as I work for a non-profit and do a lot of communicating through email. It's not useful when I can't access my mail! I don't want to switch browsers and I don't want to have to switch email (to Gmail or something) - but SOMETHING'S GOTTA GIVE!

HELP!!