Interface graphical glitch

Hi y'all,

A colleague has encountered a strange graphical glitch with the HUD interface - picture below.

http://dl.dropbox.com/u/338894/catglitch.jpg

In case there's any problem with the image the glitch is that all but the data areas of the layers window turns white - by data areas I mean the numbers and values that you enter to manipulate a layer - these are blank but can be maniuplated normally - it seems as if the HUD isn't rendering properly.

Here's the setup:

Mac Pro, probably 2007 model, with Radeon X1900 XT
Newly upgraded to Snow Leopard 10.6.3
Running a triple head to go and a single monitor for programming.

My colleague describes the glitch happening only when she accesses a mix currently assigned to the Centre output of the triple head. It's running at 2400x600 @ 60Hz

Any pointers welcome! My suspicions are that it's related to the X1900 and snow leopard, but I'm not sure.

I've found a firmware update for the X1900 but I'm not on site to see the problem or install the update.

Thanks folks
Tim