Try this and see if it corrects the problem.

Disconnect your printer. Download and run this patch and completely remove the printer from your computer.

Restart your computer.

Download the proper drivers.

XP Drivers

Vista 32-bit Drivers

All other drivers

Install the proper drivers. You'll be prompted when to connect the printer(powered on)

Scanning

Scanning using USB connection, open the Dell All-In-One Center, click on scanning and copying and scan from there.

Scanning wirelessly, use the scan buttons on the printer.