Canon MFP 8350 slow scanning via ADF

Windows 7; Canon MFP 8350; Scanning through ADF is extremely slow at one of our sites. It literally takes 10-15 minutes per page to process. Same if pushed from the scanner (computer to scan to is selected at the scanner), or pulled from the Canon application on the computer. Same if scanned to local computer or network share. Same with any user at that site. Same with any format they scan to (PDF, JPEG, TIFF). No network jams or any slow file/internet/etc. access otherwise. Scanning is acceptable if using flatbed-one-page-a-time scanning. Rebooted scanner, power-cycled too to no avail. Thanks. Alex.