Question : Remote Desktop not working via IP address

I have two PC's that are not allowing Remote destop connections via their IP addresses.  I can remote desktop onto them from within the LAN using their PC names, so all the functions of Remote desktop must be working.  I have several other PCs on the LAN that can be accessed via their IP addresses.

I have checked that the users are enabled for remote access, and that the PCs allow Remote desktop, but presumably this is all irrelevant as the PCs can be accessed via their names.

I have assigned DHCP reservations to the IP addresses they use, so I know these are not changing.  I have tried changing the public port numbers that identify them within the Belkin router.  

The only two thing these PCs seem to have in common is they are both WinXP, all the other PCs within the LAN that work are Vista, Windows 7 or SBS 2008, but I think this is a red herring.

Both give the same error message "Remote desktop can't connect to the remote computer for one of these reasons:..." (none of which are right because remote desktop does work via the PC name).

Any suggestions short of upgrading the OS?

Answer : Remote Desktop not working via IP address

Im not sure if its called the same thing in the newer server but in 2003 its at the bottom and called Group Policy Results. it will be empty if you click it but right click and choose group policy results wizard which will allow you to specify user and computer to run the results on. that will create a report that will then be listed under Group Policy Results and that shows all GP that affect that pc with that user/all users