I think I had a very similar problem!
The scanner of my all-in-one HP PSC 1510 just stoped working. I uninstalled the driver and tried to re-install it. But it didn't work. Then nor the printer nor the scanner worked. I chated with HP support but had no success.
I had to restore the system to a previous date. At least the softwares came back.
I have now the printer, but the scanner isn't working. I've downloaded the hotfix KB940199, but when I'm running it, it says it isn't compatible with my system (I think it may be because I updated to the Service Pack 1 [Vista]).
Something about the DOT4USB thing appeared here also.
What can I do?