I have a Debian 5 box running kvm with multiple host vms (5 Lenny, 1 XP and 1 2008R2). The problem I have is that none of my guest VMs are able to access the network ...

I don't have the exact specs on the host system, but it's a fairly new machine, 4 dual core HT cpus, a bucket of ram, and a fiber/san back-end. Running KVM on RHEL5 I think. The guest system is ...