With qemu version 1:2.5+dfsg-5ubuntu10.37, I rebooted a guest with a normal network interface, and after the 2nd reboot it lost networking. Then upgraded to 1:2.5+dfsg-5ubuntu10.40, stopped and started guest, and rebooted it 10 times without any networking problems.
With qemu version 1:2.5+dfsg- 5ubuntu10. 37, I rebooted a guest with a normal network interface, and after the 2nd reboot it lost networking. Then upgraded to 1:2.5+dfsg- 5ubuntu10. 40, stopped and started guest, and rebooted it 10 times without any networking problems.