It might help if you say what application you are using but I presume you mean Internet Explorer.
I get this on NT using MS Office 97 while my PC at home works fine, if I minimise the window then bring it back up the graphics sort themselves out for a while. I had always thought it was something to do with the graphics card or the drivers. Our IT guy just mumbled something along the lines of "well it happens on my PC too!".
I'll be interested to see what the guys at this site come up with.