FWIW, I was reminded of your issue here while I was reviewing past issues of MacWorld magazine following my recent return from "far far away" where I don't get mail......the March issue, specifically on p.46, cites a couple of good work-arounds but also led me to believe that my All-in-One would no longer scan now that I was using Snow Leopard....a "fact" that didn't seem to ring true to me, as I had used the scanner many times since updating my OS.
It turns out that my HP 7680 OfficeJet Pro works just fine under Snow Leopard (currently at 10.6.4).....HP Scan Version 2.1.3 (7) is the software driver that I have installed and it has never had a problem with Snow Leopard.
My AIO lives on the LAN as an IP device with a dedicated IP address and I access it without wires from anywhere in the house using WiFi.
The specific HP site with the full details lives **HERE**
Hope this gives you some hope....