My machine is rebooting after Darktable runs for 10-30 minutes. I think it is the videocard but from the list they say it can be a number of reasons it does thiis. What can I do to nail down the reason for the reboot/crash (did I mention that sometimes the system crashes)?  The reason I think it is the video card is because it only restarts when I'm running darktable and have made a few modifications to the image. I would hate to replace the card only to find that wasn't the problem. This crashing thing only recently began.
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