suse 9.2 pro with 8 GB ram

About a month ago I had a problem installing suse 9.2 pro on my dual opteron system. It's a tyan S2885 motherboard with 8 GB ram. I was asked to try mem=2048m as a boot option and that worked. Everything installed fine. A few days ago I removed the mem=2048m from the grub boot options and now it wont boot. I can get it to boot again by re-adding the boot option but then I only have 2 GB of ram not the full 8 GB that I need. Suse 9.0 and 9.1 worked fine with 8 GB ram. Does anyone know what the problem is? Mark