Sometimes with HP printers a print job will get stuck in the print queue [a spooler problem]. You can usually tell this is the case if the printer icon in the lower right shows the job printing, but the page number oh the left is usually higher than the number on the right, ie 6/1. Sometimes deleting the print job will work, but other times it gets stuck and the only remedy for that is to turn off the printer and unplug both the cable from the printer to the computer and the power cable from the back of the printer, turn OFF the computer, wait 30 seconds to 3 minutes, plug everything back in and then boot up the computer. That should completely clear out the print job and you can try again.
HP has a
diagnostic utility tool that can help with this if your OS is Vista.