If you had a PC with a locally-attached printer and you made an RDP connection to a Windows 2003 server running terminal services, the printer would automatically show up and be available for all other RDP sessions on that terminal server. We have the same scenario, but now with a Windows 2008 R2 server running terminal services. The result now is only the directly-connected PC can see and print to the printer through the RDP session. None of the other terminal server sessions can see printers that have been redirected through other client sessions. I've gone through the steps to enable printer redirection via terminal services. The correct drivers have been installed because remote/redirected printing is fine from the RDP PC that has the printer physically connected. The printer has been shared on the hosting PC.
It's almost as though there's a registry setting that needs to be tweaked to enable RDP Redirected printer sharing on Windows 2008 and it was enabled by default on Windows 2003.