In your kvm command line above, it says "file=/var/lib/libvirt/images/LinuxISOs/ubuntu-8.04-server-i386.iso". So I'm guessing its at least not the exact log that failed (since you mention centos 5.5 and 5.6).
Also when the guest crashes, could you get a dmesg ?
In your kvm command line above, it says "file=/ var/lib/ libvirt/ images/ LinuxISOs/ ubuntu- 8.04-server- i386.iso" . So I'm guessing its at least not the exact log that failed (since you mention centos 5.5 and 5.6).
Also when the guest crashes, could you get a dmesg ?