Windows Live Messenger and System C.P.U.

When I Sign In to Windows Live Messenger, my C.P.U. is up at 100% and hovers around 90% and higher.  Just want to check if anyone else is experiencing this.  And does anyone know why this happens?

 

 

 

Norton Internet Security 2009

Windows X.P., S.P. 03

Windows Live Messenger, Version 8.5.1302.1018