Hiya, this problem will be because you have probably got an Intel 945GM Express chip set and of course a version of Vista. Since upgrading to Vista I was getting this problem too on my Dell Inspiron.
I fixed mine by ensuring I have the latest driver installed (7.14.10.1147 for mine). This should install the configuration tool. The problem seems to be to do with the Intel Display Power Saving Technology. Disable it and all works fine. To do this, from the config tool, select the display settings option, click the power settings button and disable it.
Worked for me. Hopefully it will for you too! Let me know if it does.
Cheers.