I have had it! Before the August release of Snow Leopard I had a working HP Scanjet 4850 scanner which is about three years old. Since I installed Snow Leopard, I now have a large paper weight. HP has been promising for months to have an update for the scanner drivers (along with many other models) with their own deadline coming and going, and to date has delivered ZILCH. I have tried removing all HP software and drivers, then reloading everything and the same result, no scanner recognized.
Today, I tried something different, I moved the scanner over to the netbook with Windows 7 Home Premium on it. Not only did it recognize the scanner, but installed the drivers automatically. Unfortunately, this will have to do for the time being, since neither Apple or HP seem to be interested in anything but selling new hardware and software. I have poured over their support sites on a regular basis for an answer, and nothing other what I have tried.
This experience has made me resolved in one thing, I will never buy a HP product ever again if this is how they support their products.
Core Duo Intel iMac 17" OS 10.6.2 Snow Leopard and a MacBook 13" 10.6.2 Snow Leopard, Telephone DSL modem/router, 8GB iTouch OS 3.1.2, Acer AspireOne AOA150-1029 Windows 7 Home Premium