Troubles with KVM... Anyone got a version working?

Dear Planet Ubuntu, I've been having issues with KVM for several months now (running Ubuntu Hardy LTS). I was using kvm62, had many issues with it (non fontional SMP, issues with network drivers, ...), then I moved to the kvm84 and libvirt 0.6.1 backports, an still am experiencing many issues - the worst being regular crashes of virtual machines, which isn't exactly fun. I thought I had fixed it (my 32 bits vms were running on 64 bits kvm processors, which should work, though.. but they are now crashing with a 32 bits processor as well).  This is what is produced by munin when the VM crashes.

Dear planet readers and KVM users, what version of Ubuntu are you running with KVM, and with what version of KVM/libvirt? Are you happy with it? I am getting somewhat desperate