Why is one of my Yahoo email accounts extremely slow while the other isn't?

I have two Yahoo email accounts. Both were working just fine and suddenly last week one started timing out. Getting my mail is a frustrating chore. I've switched from the classic to the new mail and that didn't help even though Yahoo Help suggested it would. Now it's simply frustrating in a whole new look.
Why is one of my Yahoo email accounts extremely slow while the other isn't?
Yahoo is still having some problems at the moment. Suggested cures range from Update Adobe Flash Player and Javascript to clear IE7 cache, cookies, and browsing history. Different things seem to work for different people. It's causing attachments to not show, 999 errors where it won't let you do a particular action and some people cannot send receive delete or move mail. It's not just Vista either it's happening to some of us on XP. I have been advised to use this site to view my mail, www.mail2web.com if all else fails go back to classic mail via this link. http://us.mg1.mail.yahoo.com/dc/optout?s... click yes when asked do you want to opt out. Hope this helps.