Office XP anomalies

Currently we are experiencing a problem in our Academic Labs. When the students are working in any MS Office XP product, they will some times get screen anomalies.

An example is at the following address:
http://www.delta.edu/gtmead/anomalscreen.doc

The white boxes that you see in the picture are actually occuring on the screen. We are using SP2 for Office XP, The hardware is all Dell equipment but is as new as 6 months all the way down to 3 years old. Does anyone have any ideas what is going on with this issue?