I had the same problem and can give you the exact instructions I was given and used to fix mine. I am not a tech guru so do not have all the underlying reason about why.
A link will be provided. It is the place to download the updated version of the Lexmark Driver for Vista, whether it be 32 bit or 64 bit, or even Windows 7, etc.
The other thing I had to do was to update Vista; in other words short of a full reinstall of the Vista software is the only way I could get it to work. Do not plug the cable for the Lexmark hardware in until the Vista has completely finished doing the update. If you do update instead of full install with the Vista disc, you can still keep all of your docs, etc.
Link for Lexmark updated drivers:
1. So to recap: delete all of your printers in control panel.
2. To a complete update with your Vista installation disk.(Make sure the cable to the Lexmark printer is unplugged until Vista finishing installing itself.
3. Install the updated software from the Lexmark link.
4. You may still have to use the Lexmark original installation software to tweak some items for the different applications such as fax versus scanner versus copy, but the main problem for me was no printer or scanner working. I do not use it for fax since I have Efax, so that was not an issue for me.