I am also using Windows Live OneCare and the OneCare firewall allows the Remote Desktop connection - however, I can also use Remote Desktop from Windows because I made changes in OneCare.
Open OneCare.
Click Change Settings
Firewall tab/advanced settings button
Ports and Protocols tab.
Find the two options for Remote Desktop and place a check mark on both of them.
Close the dialogs and it should now work for you.
-steve
Microsoft MVP Windows Live / Windows Live OneCare & Live Mesh Forum Moderator