Yesterday, we were having the same problem however the test page printed perfectly. Today is a new story. The test page now just printed the 4 color Windows flag thing and nothing else. Strange thing is the Windows flag was not on yesterday's test page.
I am assuming that you still have the original setup CD and have access to the internet to dowload the updated full install if there is one available.
Then unistall the printer completely. If you know where the original install files were placed, make sure that they are all gone, then reinstall the software for it.
Take a look around inside the printer to the extent that you can and make sure no bits of paper are stuck in the sensors that trigger the paper feed and in cartridge.
You didn't say how old the printer is. If it's more than a few years it should last longer than this. HP quality and reliability has suffered a bit in the last few years (management issues).
I would still buy another HP if I needed a printer. Hang in there.