This can be one of two things. (Both effects might even contribute to the problem at the same time.)
An analog timing problem, if the signal goes through a VGA link.
A so called inversion effect which is inherent in how LCD panels are driven, which makes certain types of pattern behave badly on different models of LCD panels.
Here's a page which both explains these problems in detail, and offers test images to figure out which problem is happening for you.
As Turbo J suggests, you should definitely try to use a digital link all the way, if at all possible,