Thanks for your reply Greg.
Go into System Preferences Print & Fax
Remove the current Lexmark Printer and then re-add it.
Make sure you see Bonjour Shared
when you are adding the Lexmark back and of course, make sure it is the Lexmark printer on the network you see.
Once you add it then attempt to print once again.
If this does not work, repeat the procedure as listed above, except
Do not delete that printer, instead, click the IP tab and fill in that window like this:
Under Print Using:
Keep the Generic PostScript Printer
there and click the Add button.
Once this has been added, now close out of System Preferences and attempt to print using the IP address of the router as you have just set up, when you make your printer selection.
Let me know if one of these procedures helps. If not, then reply back to me as soon as you are able.
Thanks again for your patience!