I can't say I've ever experienced this. How hot are we talking? It just seems very unusual for a computer to specifically decide not to do something due to heat, unless it really is just that hot and needs to cool down. Try pouring cold water on it to cool it off a bit and see if it help. I mean personally, it's like 32' here at the moment and if someone told me to command+tab I'd tell them to naff right off. More likely to be a software issue but again, a rather unusual one to be related to heat.
First I'd try identify what's causing that heat, if it's unusually hot it's probably an indication of heavy CPU usage. If you're not doing much with it then there may be some background wild kext running amok which is causing other issues, such as interfering with keyboard controls. That's my best guess anyway, you'll have to work through the problem to clear that one up.