The is on Jaunty Alpha 6.* I can't create a virtual machine with bridged networking in virt-manager.* It works fine creating the virtual machine with virt-install.* I found a bug report for Hardy here: https://bugs.launchpad.net/ubuntu/+source/virt-manager/+bug/192605 but it says it was fixed in Hardy (which, if memory serves, I had this problem in Hardy also).
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