VMware ESXi - vSphere - Can't exit VM console access
The key combination Control + Alt solves this problem
Control + Option on the Mac Keyboard should do this for you (Option on my keyboard has an alt on it too).
I also ran into a similar problem in a Windows XP VM that had once connected to a VMware Server 1 Console, and had the key sequence changed to Shift + Alt in the configuration. That was a real pain to figure out, because the ESX console insisted that the exit sequence was Control + Alt.