cupsd configuration: service-unavailable errors

Hello,

I am attempting to print remotely using cups.  Attempting to do a 
"cupsdoprint -H 192.168.0.2:631 -P lp foo.pdf" from the client 
192.168.0.1 results in a "server-error-service-unavailable" from the 
client and the following in the server log.

D [29/Sep/2003:14:33:28 +0100] AcceptClient() 3 from 192.168.0.1:631.
D [29/Sep/2003:14:33:28 +0100] ReadClient() 3 POST /printers/lp HTTP/1.1
D [29/Sep/2003:14:33:28 +0100] SendError() 3 code=403

Printing works locally on the server, as does the web interface to cups.

I apologise if I'm missing something obvious: I have never tried to 
configure cups before.  Any advice appreciated.

Regards,
John Spray