I have been trying to follow the guidance on using Xen from Ubuntu. When setting up the bridging I followed the notes but when I restart the network my windows change and I get a recurring error message. I am unable to type in terminal and I can't run any programs. I end up doing a hard reboot and the networking doesn't startup.
I end up undoing the changes to /etc/network/interfaces and restarting. Still I can't setup a virtual machine since the bridging won't work.
This question shows some of the problems with restarting the network that I am having. If I use
sudo service network-manager restart instead my network seems to connect and disconnect repeatedly. I also noted a bug on launchpad regarding the system crash when restarting networking.