All right I got it... First of all when running in 32-bit mode, try to set 2048 mb of memory or less. Maybe 2GB is a limitation of 32-bit Linpack itself. If so, I'll add a check for it.
As for the 64-bit Linpack, it's weird and I doubt I'll be able to fix it until I install Vista 64. And this won't happen till weekend, sorry.