I guess you may need to reinstall the driver.

You may give it a try.

I'm having the same problem. Reinstalling monitor driver did not work. If anyone knows how to fix, please help us!! Thanks!!

I figured it out. The driver I needed was the 82865G Graphics Controller. You can download it @ http://support.dell.com/support/downloads/type.aspx?c=us&cs=19&l=en&s=dhs&SystemID=PLX_PNT_CEL_GX270&category=13&os=WW1&osl=en&deviceid=3841&devlib=13