Wish I could help but we have the exact same problem. Throughout the Web there are lots of complaints about this but no answers.
HP, on their tech support phone number, will take a stab at verbal solving of this for $35 up front, REGARDLESS of whether they are able to provide a solution or not. Otherwise since it is out of warranty (only a year and a half old) they will offer a modest "discount" on a new replacement printer.
Nothing "office" nor "pro" about this printer, cheap junk!