I just upgraded from engine 3.1 to 3.3 on my standalone centos 6.4 system. The 3.3 engine-setup apparently did NOT include the requisite iptables lines for port opening for the spice to function.
I did a yum update for the ovirt-engine-setup to get the latest tool. Then I ran engine-setup to let the process upgrade as required.
I added the missing ports from a second system I've not yet upgraded and all is well. Just though someone might want to look at a possible issue.