I'll commit this to beta2 right now. Mike can decide how serious an issue
it is when he gets back.
We've tried to reproduce this problem on another machine with a similar low-end Intel graphics card / motherboard, but without any luck. The bug seems to be very specific to Dell's Optiplex. Even worse, Manish has confirmed that this problem only happens with DisplayMode test and not MultiBufferDuke. I've sent him a variant MultiBufferDuke which I'm hoping will reproduce the problem. If not, we might have to simply document this and decommit from merlin until we can get a Dell Optiplex to debug.
The variant MultiBufferDuke did indeed cause the problem, which mostly narrows it down to any application that changes the display mode using DirectX more than once on this hardware. I would like to test this with a native application, but there are not enough resources at the moment.
Since this is obviously a problem with the driver on this particular harware, I am going to have the release notes amended with the information, and close this out as "will not fix".