Hello,
One thing that I can confirm is that the model of card is not certified with this model of station.
When I said that is not certified, I mean that it is not tested by HP.
The list of certified cards are available here:
http://h18004.www1.hp.com/products/quickspecs/15077_div/15077_div.pdf
Try to update the bios of your station:
if you will be able to test with one of certified model and you will have the same problem, you must call the HP support
All the Best
karim