Guest account access to network printer

Hi all

I have a problem whereby I can't get an account from an untrusted domain to print to a network printer using RunAs with the /netonly switch from a Windows 7 machine.

The network printer resides on a Windows 2008 R2 server.  Things I have done:

1. Enabled the guest account on the server.
2. Confirmed the successful use of the guest account by creating a normal file share on the print server, connecting to the share from the client (using Runas) and copying a file from the share to local (Win7) client.
3. Set permissions on the printer so that Everyone can print.
4. Set the permissions on the spool folder on the server so that Everyone has Full Control.

When I try to print, the client side rendering completes successfully, but I get a "Access Denied" status in the printer properties when viewed from the client.  Nothing helpful appears in the print server logs.

Any thoughts on what else to try?

Alexei