You may be going through what I just did. I have a HP DeskJet 1220c and first I tried to get it to work with my LinkSys print server using the parallel connection and gutenprint. The install looked/sounded great and I can print a test page from the print server's utility, but could never print anything like an email or other document.
So I switched over to a USB right to the back of the iMac. I went to HPs web site and they won't allow you to download drivers as they insist that the drivers are already in the OS. Someone responded with a link to a driver page and I downloaded what appeared to be the right driver. I installed and removed the gutenprint driver, but the pop-up printer dialogue I get now is nothing like the one I get with Windows XP. It's like a junior league version, something truly less than basic. In Windows, I'm given choices for dozens of different types and sizes of print paper, different quality levels, bleed options, registration marks, and all sorts of print information. This driver gets it to print, but rather poorly and it looks like its at lower resolution as well.
I'm going to try and get some tech help from HP, but they will probably moan about the printer being out of warranty and therefore it'll cost me $75 a session to get help. I don't know if anyone here or in other forums have had similar problems, but its worth bumping your post a few times.