Why am I unable to reconnect to a Remote Desktop?

Question

I have some home media services like pyTivo running on my Windows XP machine, but they only run when I'm logged in.

While I'm on my Windows 7 machine, and I use Remote Desktop to control my Windows XP machine, everything is fine, until I'm done working in it and want to leave (by "leave" I mean that I want to close my RDP session, but leave it logged in as me so that the services continue).

Two options are available:

1. Log off - I don't want to log off, because then my services will stop.
2. Disconnect - If I disconnect, it won't let me back in; it's as if the computer has locked itself off the network. To resolve this I have to go back to the Windows XP machine in-person and log myself back in.

The connection is via a wired home network.