Usually for a Dell AIO printer, it is suggested to re-install the printer like it's listed below. It usually fixes the problems involving scanning and printer communications. Should work for your Lexmark printer, since most of Dell's printers are Lexmarks.

Disconnect your printer. Go to start/programs/Lexmark printers and un-install your printer. Check the control panel and make sure it's removed.

Restart your computer.

Now go to here. Download drivers, Utilities, firmware and Patches. From what I see, the patch is to remove the printer.

Install your printer. You'll be prompted when to connect it.

Then the Utilities and firmware.