Update: 3 hours later
Unplug the USP cord to your computer from the printer
Go to System Prefs
Open "Print & Scan" icon
In the left column, you will see listed your printer, but the driver doesn't work with Mountain Lion
Right click on the printer's name, hit the delete or minus button. Delete all the printers listed if you have to.
Install the new printer driver software
Plug the USB cord back in. Now you should see the old printer listed again in the left column - except now it will have a new driver compatible with ML
Choose a page to print, open Page SetUP, choose your printer
Go to "Print" and print your page.
Mine worked for me!!! Hope yours will too.