Simple question....I hope

Hi, I have a PC with 2 Intel Xeons and SuSE 9.1 installed, I use a piece of software that regularly uses up all free RAM (1Gb installed) and crashes the whole machine. Now I expected this software would need a lot of RAM, so created a 2Gb swap partition when I originally installed the OS. The problem is that SuSE *never* tries to use swap and consequently the machine crashes every time I try to run my prog. If I run top whilst running the other prog: free RAM goes down, swap usage stays the same at 0kb, always.... :( Is this a "known bug" - or is there something else I should be looking at to try to fix this? Any help/suggestions much appreciated. Cheers, Jon.