When I enter my Mac's IP address (192.168.0.103 for Ethernet, 192.168.0.4 for Airport) under "Printer Address" and enter the name of the queue (EPSON_Stylus_Pro_R280" under "Queue" the "verify" button in Desktop Printer utility gives me "printer not verified."
As you could have read in the topic I linked to in my post above, that is exactly what happens in my setup. No solution I can think of.
You can try to set up a desktop printer that prints to a PS file in a folder in the shared folder that has a folder action script assigned to it that will print the file to your default printer. That setup should work always. It is all in that same forum topic about printing. http://www.emaculation.com/forum/viewtopic.php?t=3331
Incidentally, I am unable to paste into SheepShaver anything copied into the clipboard on the OSX side. emendelson says to do that in copying over the queue name.
As is described in both ReadMe me with SheepShaver and in the setup guide, this is one of the issues with running SheepShaver in 64bit mode. When you set SheepShaver (in Finder Info) to run in 32bit mode, you can copy and paste text both ways (though not to or from some applications).