I’ve been having lots of problems loading Yahoo mail lately. It started with Firefox 2.0.0.4. All of a sudden I just couldn’t get past the login screen. Nothing would display. Nothing in the source, no errors. Just nothing. So I started using IE to read Yahoo mail. Then I upgraded to IE7, and Yahoo Mail became unstable again. Random HTTP errors. So it became unusable again. I cleared my cookies, cache, and removed my adblocker extensions. It just got worse and worse.
So yesterday I logged in on my trusty Mac, and switched from the Yahoo Beta to the standard Yahoo. I’m back in business everywhere now. What a shame. I hate the old style, but it’s the only version that works.
I’ll just have to use Gmail as my main free email now, and relegate Yahoo to the spam email system.
Ali's Stuff 
If anyone can help me figure out how to get the new Yahoo mail working in Firefox, please let me know. I just tried switching back, and still nothing. It doesn’t load. Most annoying.
i have the same problem i done everything yet no answers pls help
I haven’t found anything on the net that gives me a clue as to what’s wrong. I’m sure there are lots of people experiencing this. It’s not just on one machine, or browser, so it’s a fundamental thing going wrong with my Yahoo account. If you can switch back to the old style interface, that works, though I hate it.
how do you switch back to the old style interface?
Log into Yahoo Mail and you’ll see at the top a small blue link for “Mail Classic”. That will switch you back to the old Yahoo.
I don’t seem to be having these problems anymore, and the new mail client is working fine.