There are reports in the Microsoft Knowledge Base about a couple of AOL programs that aren't compatible, with some computers, but I haven't heard of any from Yahoo like that. Maybe they've blocked your sending 'cause of that SPAM you've been putting out ;-(

Seriously, a change in your login might make them think you've been robotized, and some services will block sending until they decide you're safe. I don't know how one gets help from Yahoo, but with hotmail the only way is to send them an email if your email isn't working.

John