At work I've got a HP LaserJet P1505n printer that is used as network printer. It has an ethernet port and is plugged in directly into the network. Everybody in the office is using Windows and has no problems working with it.
After a few hours of google-ing, I also managed to set it up with CUPS as a LPD printer, with some problems: every time I send a document to it, it goes into the "error" state, and I have to press the "green" button for the printer to start printing. Is there a way to work around these errors? I tried to google for these kind of errors, but couldn't find anything useful. Thanks for your attention.

If you don't have HPLIP installed, I'd suggest getting it and using it to install/reinstall/test the printer. It seems to work very well.

I know it's available for Debian, because I'm using it on my Debian box. I've also used it with Slackware and Ubuntu; it's done wonders to improve my opinion of HP as a corporate citizen.

The GUI interface is called hp-toolbox.

frankbell, I have HPLIP installed, but when I try to install a network printer, all the options available, except USB connection, are greyed, without the possibility of choosing any.

I have not run into this problem, so I'm fresh out of ideas, but I have a thought:

If you are running a firewall, have you opened the TCP/IP ports in it? I'm just guessing here, that should not be necessary for outgoing, but it might be necessary for incoming messages back from the printer.