I don't think this is a heating issue.
I have both CS4 and CS5 installed, and if I use CS4, there is no problem.
But if I use CS5, the problem occurs.
If it's an overheating issue, it should happens to CS4 or other applications too.
The fact is, as long as I don't run CS5, no matter how long the computer has been in use, there will not be any problem.