This is just a quick workaround.
After restarting my Ubuntu 10.04 server KVM virtual machines didn’t start. Tried manually:
virsh # start saturn error: Failed to start domain saturn error: internal error unable to start guest: chardev: opening backend "pty" failed
I needed a fast solution. Very fast googling and this gave me a clue, that something with virtual serial or parallel ports is wrong. So I just removed these unnecessary lines from config file:
<serial type='pty'> <target port='0'/> </serial> <console type='pty'> <target port='0'/> </console>
This workaround works for me 
