I started off using View 5.1 but have noticed the same thing. I've been installing the View Agent on physical boxes for those not ready to make the leap and get rid of the VPN requirement.
I created a thread with the symptoms and steps to reproduce it. Maybe they are the same as yours? I currently have a case open with VMware.
http://communities.vmware.com/message/2168885#2168885
It doesn't look good that View Client can't connect but MSTSC can. Not a good first impression when I tell them to logoff before going home to avoid issues. For many in IT, logging off is not a small task.