I was having the same exact problem, and I posted a link. Amy, a Yahoo! Advisor asked if i was running Windows Blinds, which I was. You will need to go into WindowsBlinds and do a per application setting exclusion. It’s the top check mark for total exclusion. After you do it, you will need to close down and exit Yahoo! Messenger, and sign in again. It should work now!!
Well Amy,
You ROCK!! That was the problem!! Thank you so much!! I am sure alot of people are having this problem and this was an easier fix than I thought it was going to be!!
Thanks again!!