I had a similar problem where neither of my printers would be recognized. I ended up taking it to the genius bar, where they tried several things that didn't work. They ended up doing an "Archive and Install" which fixed the problem. I'm not sure if you're familiar with this procedure but it's one you can do yourself. Basically it is re-installing OS X while keeping your files in tact. I would back them up just in case though if you decide to try this.