Description of problem:
Sometimes when I try to start one of my VMs, I get an error dialog saying "Error starting domain: internal error unable to start guest: qemu: could not open serial device 'pty': No child processes" and showing this traceback:

Traceback (most recent call last):
  File "/usr/share/virt-manager/virtManager/engine.py", line 571, in run_domain
    vm.startup()
  File "/usr/share/virt-manager/virtManager/domain.py", line 664, in startup
    self.vm.create()
  File "/usr/lib64/python2.6/site-packages/libvirt.py", line 293, in create
    if ret == -1: raise libvirtError ('virDomainCreate() failed', dom=self)
libvirtError: internal error unable to start guest: qemu: could not open serial device 'pty': No child processes

I'm not sure where to file this, but I'll start with libvirt...

Version-Release number of selected component (if applicable):
qemu-common-0.11.0-3.fc12.x86_64
kernel-2.6.31.1-56.fc12.x86_64
libvirt-0.7.1-10.fc12.x86_64