Problem with solving large models

Hi,

Lately, I've been trying to solve transient, non-linear heat conduction problems with ~500,000 elements. I've noticed that my computer seems to stall during the solution step and was interested to know what might be happening and how to resolve it. I'm using Redhat Linux. When I use the command "top," I can see that 80+% of my memory is being used but <10% of my CPUs are being used.

Do you know why Comsol is having a problem?

Thanks,
Kevin