Multiple CPUs causes blue screen on Windows guest (14.04 regression)

Configuring a Windows 7 guest using more than one CPU cases the guest to fail. This happens after a few hours after guest boot. This is the error on the blue screen: 
"A clock interrupt was not received on a secondary processor within the allocated time interval"

After resetting, the guest will never boot and a new bluescreen with the error "STOP: 0x0000005c" appears. Shutting down the guest completely and restarting it will allow it to boot and run for a few hours again.

The guest was created using virt-manager. The error happens with or without virtio devices.