Memnon I figured I'd post this considering you locked up multiple times last night in the TA. Here's a list of things to do to find out what the problem is.
For starters take your case sides off and spray out all your fans with compressed air. You can get this from most electronics stores. It'd be wise to also spray down all your cards and motherboard and your power supply fan. You dont' need to remove any one of these to do this.
Once you've sprayed out all your components your going to have to check your fans to ensure they are still turning and not dying out on you when put under a load. Basically run AH2 or any graphics intensive program. Keep your case sides off and when it's starting to act up look at your graphics card fan. It could do this under normal desktop functions tpp if the fan is going out prematurely. So if you sense that the computer is opening programs too slow or see any abnormal delays immediately check your fans, starting with your video card fan.
If all seems to be well with your fans when it's starting to act up your going to need to test your memory chips. It's possible they could have thermal issues and are causing your slow downs and even lockups. If you have multiple chips remove all but one and run the system for awhile. See if it acts up and if it doesn't take that chip out and place a different one in and do the same thing. This should give you a good start to finding your lockup issue.
One thing to remember is if you've got your case sealed up in a desk area you need to be sure it's going to get enough airflow. A three sided holding area may not allow alot of air flow. Try taking the case and setting it out in the open. If you plan on sitting it on a rug surface though be sure to place a flat board or something underneath. Reason you need to do this is your forward fan slot typically grabs air from the lowest portion of your case front. Typically right at the bottom between the metal case and the plastic front piece. If you've got a fairly thick rug you may block that air flow.
Hope this helps.
