I had this same problem and it doesn't look like anyone else has solved it yet. I spoke with tecnical support and got it resolved.
I have windows vista so your instructions might be slightly different.
start> computer> double click the C folder> drivers> printer> 1200(or whatever series printer you have)> applications> then the set up folder with the CD icon.
It will install the scanner software. Also, the website has been updated on lexmark so that includes the all in one software now. So, if you have the older version from 2008, then delete the old software out of your printer folder and go to lexmark and install the new one.
Any other questions, email me. [email protected]