Stupid remote desktop not working

Okay my remote desktop doesn't work.
I get Becuse of a protocol error detected at the client (code 0x1104).
Have checked on are ISA server and you can see the connection to port 3389 being opened, I can also telnet to the port.
You can also establish a remote desktop connection on the server eg if I put localhost in it works, but from every other PC I now get the above error message.
This was working, and then it wasn't, but everything seems okay.
I have a hunch it's something to do with ISA as ISA 2004 runs on this server. As we can still remote desktop on to other servers from the same client PC's.

So it's not a problem with the clients as they can remote desktop on to other windows 2003 servers, its not a problem with remote destop as it works from the server, so it's something to do with the connection.

Am very stuck.