I had this problem on my MacBook when I upgraded to OS X Lion. Thought I had it fixed a while back but have been fighting with it most of the morning. Unfortunately, above did not help.
What did help was going to:
HP.com.printers / Product Support / Online Support / Enter your product # (series) / choose your printer from the list you get after the series # / What do you need / solve a problem / pick your problem / scan / error....
(Hope the above makes sense.)
You will have to uninstall your printer and get a download from them to reinstall.
I hope this works for you. Believe me, I understand your frustration!