Comment 14 for bug 1305191

Hold on, I see:

> wwozniak@wwozniak-PC:~$ qemu-system-x86_64 --version
> QEMU emulator version 2.1.2, Copyright (c) 2003-2008 Fabrice Bellard
...
> wwozniak@wwozniak-PC:~$ qemu-system-x86_64 -machine help
> Supported machines are:
...
> pc-i440fx-2.1 Standard PC (i440FX + PIIX, 1996) (default)

This suggests that you have a custom built qemu in your PATH
which is not in libvirt's PATH. What does

which qemu-system-x86_64

and

/usr/bin/qemu-system-x86_64 -M ?

show?

My guess is that virt-manager uses qemu 2.1 from your path to
detect machine types, chooses the newest available, then asks
libvirt to start that VM, but libvirt runs the 2.0 qemu which
can't start that newer machine type.