Just saw your post. Have you tried removing completely the PRISM card and (a) re-inserting it in the original slot and (b) into another slot.

The next step is what version of the software do you have? Maybe download the latest V1.5 as maybe the ROM's have become corrupted.

Then maybe your RAM chip is faulty once the system warms up.

Finally it could be your CPU chip or PCB breaking down once it warms up. I am assuming the CPU fan is working all the time.

Let us know how you go