Yahoo messenger 8.1

Hi, my mom is having problems with yahoo messenger 8.1 and she got it right after christmas. Also we bought her a brand new monitor. Its a optiquest viewsonic lcd monitor.
We also downloaded the new firefox for her to use instead of IE.

When ever she signs into yahoo the color bit on her monitor goes nuts. It flickers and snaps and goes black then turns to 8 bit only. she can then reset it to normal bit and it will stay good untill she signs out. Then it repeats again, and she has to reset it.

Please if you know what may be causeing this let me know

Thank you
Ros

 

Probably Yahoo Messenger. I had to stop using it because it was going crazy and running 100% processor usage randomly.