I also get this. On a second machine I tested against now (both standalone test servers). both hosts had been running VM's for about a month on version 3.0 and were updated in the normal way (aptitude update && aptitude upgrade). Both servers threw this error. first server was upgraded when spice was still only in pvetest, second server once spice had been moved out of pvetest. The first server was reinstalled after seeing this error and upgraded from fresh install before having VM's put on it and Spice worked perfectly that time.