Just something I came across last week on a SBS 2011 setup; the current version of HP’s CDP software refuses to recognise a newly-inserted RDX cartridge if you’re connected to the server via RDP. This had me puzzled for a while until I connected a monitor, keyboard, and mouse to the server and logged on there. The new cartridge was recognised instantly.
Hopefully they fix this soon, as it’s an issue in headless server setups. I’ve gotten around it for now by using LogMeIn on that server.