I'm afraid this is indeed heat related. I can tell you for sure the box is over crowded. This tower holds 4 hard drives, and 2 cdrom drives a wireless and ATI PCI cards... so the interior is pretty much filled to capacity. Of course, I did add fans to try to compensate for the extra heat generated by these devices. It has a total of 5 fans.
1 in the front of the box blowing directly at the hard drives
1 on the CPU heatsink unit
1 on the back of the box blowing away the heat from inside
1 mounted on top of the box blowing directly on the RAM modules
1 mounted on the side cover blowing heat away from the interior.
Oh.. and that's not counting the one on the power supply...
To top it off, I've opened both side panels on the tower to allow more air to flow through it, I know..rendering the side fan useless, but I figured it was worth a shot, and still the problem persists.
I should also mention that the LED's on the front panel indicate the interior temp in C units and generally read between 35 and 42 degrees. Does that sound abnormally hot?