Repeated power-save mode with 2408WFP display and Windows XP SP3

I have been using a 2408WFP display connected to a Dell laptop via DVI through a docking station with XP SP3 .  Very recently a problem came up where the monitor is constantly switching in and out of power save mode.  After some experimenting,  I discovered that this behavior only occurs when I have a full-screen window open.  If I have only partial windows open,  the behavior never happens.

Bizarre...  Since this just started occurring the last week or so,  I suspect some patch pushed by our IT department is the culprit but I had no lock searching for any information on this issue.