Weird crashes

[Baldur Gislason]

I have a computer running FreeBSD 5.2.1-REL, I've tried 3 different video 
cards (two nvidia and one matrox), I've tried two different motherboards 
(Aopen AK77-8XN and Aopen AK77-600GN), I've tried using just a single memory 
DIMM out of the two, I've tried two different processors (AMD AthlonXP 2500+ 
1.83GHz and AMD Duron 1300MHz).
I also tried moving the swap partition on a different hard drive.

The problem is this:
Programs crash, namely Xfree86.
Xfree86 always stops on signal 6 (SIGABRT), and it seems to happen mostly when 
I've filled the RAM and have started to use quite a bit of swap. I'm mostly 
filling the ram with lots of browser windows opening heavy graphics off the 
network.

Any debugging ideas?

brgds.
Baldur Gislason