kvm, failed to start network default in virsh

xxx@yyy:~$ virsh net-start default
error: Failed to start network default
error: internal error '/sbin/iptables --table filter --delete INPUT --in-interface virbr0 --protocol udp --destination-port 69 --jump ACCEPT' exited with non-zero status 1 and signal 0: iptables: Bad rule (does a matching rule exist in that chain?).

in messages:
Dec 27 23:15:39 yyy libvirtd: 23:15:39.512: warning : networkAddIptablesRules:850 : Could not add rule to fixup DHCP response checksums on network 'default'.
Dec 27 23:15:39 yyy libvirtd: 23:15:39.512: warning : networkAddIptablesRules:851 : May need to update iptables package & kernel to support CHECKSUM rule.

and there is no virbr0 interface.

Virtualization, KVM hypervisor

I started to explore KVM as full virtualization solution for Linux. The mail idea to sturdy different Oracle option on different platforms and emulate failure events to work out backup and recovery. Configuration and tuning is important part as well. So, I chosed KVM under KUbuntu 10.10. and started different installations. As I expected later there is a problem to communicate two virtual machines to each other. I asked google but didn't get definite answer. Accidentally I've found a solution lies in the plane of IP filters.