Sorry, I was thinking the APEX 2800 cards were related to this, but that was a different ticket I was thinking of. So scratch that.
As far as this problem goes, I have seen this issue happen numerous times. It only happens with users with dual monitors. Here's a workaround: Control Panel > Mouse > Pointers > Scheme > Select a non Aero scheme
It took VMware quite a few months, but they finally generated a KB for it and closed my ticket: VMware KB: Zero client monitors will randomly go black for 1-2 seconds