It sounds like a simple ventilation problem. If the component does not get the air flow it gets hot. I do not have any lap top sitting directly on the surface of anything, I have them all proped up by something to allow air to move under and around. DT replacements get hot and will do a melt down if you dont do it.
You can also when you take out the card, and take a sniff at it you can smell the burnt element, you dont have to see it. Sometimes what burned can be as small as a pin hole so visual cant always work.