I have a couple Server 2008 R2 boxes that, when accessed using RDP over 3G VPN connection, display a black screen.
Couple things that I have noted:
1) When using RDP (same laptops) within the LAN, there is no black screen and it works fine. I feel this rules out the destination servers, as well as the operating system configs on the laptops.
2) I have tried the RDP compression settings fix (group policy), disabled bitmap caching, tried using a lower resolution and tried "control+alt+end, log off and log in again" fix without success.
3) The VPN itself is healthy as well, as the laptop users can access everything else while out of the office using it. It is literally just RDP that is not working as expected.
So, keeping the above in mind, I still feel that its a VPN issue, but specifically around the RDP protocol. As far as I understand it, nothing has been changed on the firewalls, etc and anyways, the connection is reaching the server, it just results in a black screen.
I am stumped. I was thinking it could be the 3G connection, but since the VPN establishes perfectly, and they can access all other services through it (except RDP), I have doubts.
If anyone could help me out or give me some things to check, I will be grateful.