I'm having a pretty bizarre problem with a Terminal Services server used for RemoteApp. In our network the server works as it should, but at a client's office if two users log in simultaneously, the first one gets disconnected as the other one connects. The users belong to the same group but have individual users. The similar configuration works fine for all other clients.
About the server, it's Windows 2008 SP2, no AD, SSL encrypted connections. Event viewer shows no useful information.
Any hints where to start debugging? Do you need more info about the setup?
EDIT: Ok, so the problem has resurfaced with another pair of clients. Similar setup: two users, one group, more than enough CALs. Could this be a problem in the client side firewall/NAT?