Yahoo & Start-up problems

I have Windows Vista, and lastnight i got booted out of Yahoo Messanger and i
have not been able to get back in, well i thought about uninstalling the
program and reinstalling it, but now i cant get my control panel to open up
here is the message i am getting,

This application has failed to start because rvcommon.dll was not found.
Re-installing the application may fix this problem. after i click on ok,
here is the 2nd pop-up message,

::{ 21EC2020-3AEA-1069-A2DD-08002BE30309D} Class not registered

If anyone can help me with this problem i would very much appreciate it,
Thanks in advance.

Gwen