i had this error at last :
TASK ERROR: command '/bin/nc -l -p 5900 -w 10 -c '/usr/sbin/qm vncproxy 100 2>/dev/null'' failed: exit code 2
my windows was XP SP3 i remove it and install XP SP2 with java SE runtime Environment 1.7.0_09 nd it resolve , try it maybe resolve :)