Hi,
I have read about c2-users having problems with 163 upwards on parallels.
I use VMWare Fusion 6.1 and have no problems at all IF if don't have Virtualbox run before that (my wife uses it sometimes and I didn't have time to pull her VM over) or the battery is pretty low. Then my MBA goes on low everything to keep on going as long as possible.
You could try a demo of VMW6 and simply boot up your vm for testing...