Here's a long thread from the Ubuntu forums that might help.
http://ubuntuforums.org/showthread.php?t=1473570
If it doesn't, please come back with more information, particularly which version of Ubuntu, CUPS, and HPLIP, and the output of some of the diagnostics mentioned in the thread, making sure to enclose them in "code" tags, which become available when you click "Go Advanced" down there at the bottom of the Quick Reply window.
When I did the web search, it turned up a number of references to Ubuntu 12.04 and this error.
