sip/2.0 488 not acceptable here

I have a very strange issue that I am hoping someone can help or at least provide some direction:

I currently have lync 2010 set up in our environment and open for external users as well through the edge server.

I have one user (user A who cannot establish a lync call with one particular user we will call userB).  If userB vpn's into our network, user A can successfully make a lync call.  If user B disconnects from VPN, the call can no no longer be established.  Now comes the interesting stuff

Other people can establish a lync call with user B when user B is not  vpn'd in, and user b can call user A when not vpn'd in.

I enabled logging on the edge server and can see the 488 not acceptable here error code