You seem to be trying to add a printer when in the middle of trying to print. I suppose things can be done that way, never tried. However, I suggest doing it the 'normal' way and see if it helps.
1. Close any print dialogs.
2. Open Apple's Printer Utility ( probably in the Apple Utility folder ) and if the printer is already there ( which I doubt ), delete it.
Now use the "Add" button to find and add the printer, with the appropriate printer capabilities, if any, to the available printer list.
Step two assumes that you have previously installed the printers driver software, of course. But if you haven't, it will never show up, anyway...
Apple's Printer Utility is not very useful in editing any of the critical info on an installed printer, it's usually necessary to delete and re-add, especially for an IP addressed printer. YMMV for Rendezvous enable printers. And the utility Harv mentioned may make things easier, I downloaded it but never used it!