Well, could be a few factors. I don't think DVD uses more power. as far as the 75 watts, that says nothing without knowing what else you are running off that power supply.
I would try to start diagnosing this by disabling auto-start from the cd drive and see if this is replicated or not. If it is, then its probably a power/cdrom drive issue. If it doesn't come back, then you got a software issue.