I've been using a D-Link DNS-325 NAS for storage and Time Machine backup. A couple of days ago I plugged my printer into it to be able to use it over the network, but when I try to print I get error 306 (a communication error has occurred). There's also a Windows 7 PC in the house, and everything works perfectly through that. The printer does work through my Mac when connected via USB. The USB print server on the NAS is a Windows/Samba setup.
I've scoured the internet and tried all the suggestions I could find. I've deleted and re-added the printer; tried all the login credentials that I could think of (all registered accounts, "guest" with no password, and "guest"/"guest"); put the login credentials into the print server address (just to try it); set up the printer through the CUPS page, rather than through System Prefs; set up the printer through both Samba and IP; set CUPS to allow internet printing; edited the CUPS configuration file to "allow from all;" manually added the printer; and tried every iteration of the print server address that I could think of.