Hi Duncan,
I had similar problems using RDP from my laptop to the desktop in the observatory. Everything would be working flawlessly. I would have TheSky6 with EQMOD, PHD and Canon software all running and as soon as I would connect remotely. EQMOD and the bluetooth connection to the mount would disconnect instantly. I couldn't really find a fix for this so I ended up installing UltraVNC.
Using UltraVNC, I can now successfully connect and control everything inside the obs. Doesn't slow down any of the processes and is very reliable. I'm going from Vista to XP as well.
Hope this can help.
