Bottom level air circulation

I recently upgraded my box with two 9800GTX's in SLi. Everything is running fantastic except under extended periods of intense graphics I get a hard lockup with a screen and sound freeze which requires a hard reboot.

While installing the cards I saw that the lower-most card was dangerously close to the bottom of my case. In addition, the front USB, Firewire, and power/led pins are located at the bottom of the board, causing cables to be in the 1/2 inch or so between the bottom of the case and the card.

In an attempt to compensate for this, I have been running a speed controller on the GPU fans, maxing them at a constant 100%, however with the case door closed I still run into issues if I do not alt-tab out every 45-60 minutes.

Brand new user to the forums, so I'm sorry I can't provide an image yet.

is there any dust build up if so clean it out.

you could try to a a fan at the end to try cool it better.

what case have you got???

The motherboard and cards were newly purchased, so there shouldn't be any buildup.

I was considering a PCI slot cooler, however due to the SLi bridge forcing the two 9800's to occupy the top and bottom PCIe slots, it probably won't increase any bottom-level airflow.

The case itself is similar to a Thermaltake Armor Series ATX Full Tower. I have pictures on an imagesite, but I'm yet unable to add a URL to my post.

It may be a driver problem or something

I would add a fan somewhere near the base for better cooling or you could water cool your whole system.

Thanks for the suggestions, but upon further investigation it looks like the issue isn't cooling-related. I removed the side of my case and through the use of monitoring tools lockup happenings didn't seem to be caused by heat.

The lockups only seem to occur during high stress. They trigger only in specific programs, and more frequently in some more than others. AFIAK it doesn't seem to be a PSU issue as it's a hard lockup and not just an unexpected restart. I ran the Microsoft boot CD for a memtest which turned out fine and ran full HD scans using the Western Digital diagnostic tool. Going to try a reinstall of trigger programs and eventually a reformat if lockups still occur.

Any suggestions of other possible tests would be welcome.

Could be faulty ram, or the game has a memory leak.