Drop It Like It's Hot
Our HP OfficeJet keeps getting the scan head jammed at power-on. It sits there and rams the head against the housing. After checking the support forums, I deduced the #1 fix to the problem (to some extent HP-official):
1. Take the machine somewhere over a soft surface like carpet
2. Pick up the machine about one inch over the surface
3. Drop the machine
4. Repeat if desired
It worked!