Yes, plenty of people I know (I'm a computer nerd, as are most of my friends) have had a similar problem with overheating CPU's though most of them are due to overclocking the computer.
What you may want to do is create a wind tunnel by creating a vortex by sucking air into the computer on one side, and spitting it back out the other, this will help by making sure heat doesn't stay in the computer for too long, and since heat rises you may want two fans mounted at the back, on the lowest mounting area on the frame, and another at the highest, if that doesn't work, try getting a larger heatsink, you could probably pick up a large heat sink online for cheap, I'd suggest an old 200Mhz heat sink, when the 200 first came out it had serious heat issues that were solved by a 1.5"x1.5"x4" heat sink, that's right, 4" long spikes, this gives plenty of heat dissapation.
Or if you could afford it, get a freon pump and run one of the pipes through the computers case.
Also consider cooling the entire computer by adding a drive cooler too.
These were also created because of heat problems, when the first 10000 RPM drives were created they needed a seperate coolant, if you can pick it up cheap, see how it works, if it works by shooting air out of the computer, try reversing the fan and blowing cool air into the computer.
Or if you could afford it, you could get a freon based heat sink, similar to the one discribed above, and running a freon pump in between all the little spikes, so they stay supercool, and and the cpu never overheats.