Use Preview and the Import from Scanner option.
You will get the same answer on the HP website
13' Macbook Pro, 10.6.2, 4 G Ram. I downloaded 10.6.2 and now cannot scan. It will print ok. I had the same problem with 10.6.1 but used System Pref > Print and scan > hit scan button. Now nothing works. Using HPScanPro I click on "new scan" and get "unknown error occurred". Using System Pref > Print and scan I hit "open scanner" and get "no scanner selected" even though Photosmart C4500 appears in box. A few times it said "scanner warming up" and then scanned but the scan did not appear on desktop. When scanning from the unit itself, the icon bounces briefly in the dock but does not open.I have uninstalled and reinstalled the software. (By the way it is using "driver4.0.2) Please help! Thanks.