Hi, and welcome in the forum <img src="/ubbthreads/images/graemlins/winkwink.gif" alt="" />

Do you have any other progr. running in the background? Like ICQ, antivirus, music progr.,... If yes, I'll suggest you to shut it down.
And can you check if your color depth is set to 16 bit?

Maybe also have a look at our Technical FAQ Support
If this doesn't help you, let us know.