sounds like you have a bad formatter....there is a way to circumvent the formatter and print whats called an engine test. this is used just to test the mechanics of the machine and leave the brain out of the equation...
Engine Test Button Location HP laserjet
printer 5000 series
The engine test verifies that the print engine
is functioning correctly.
The Formatter PCA is completely bypassed during an
This test is very useful for isolating printer problems. The
prints a full page of lines across the entire printable area,
and is also
useful for checking and adjusting registration.
Engine test will print from the last input tray
If the last input tray is empty or if the last input source was the
then the Engine Test will print from Tray 2 (standard 250
If Tray 2 is empty (and the last input tray is empty or the last input
was the duplexer), then the Engine Test will not
function.Printing an Engine Test HP laserjet printers 5000
To print an engine test, use a non-metallic object (such as
a pencil) to
press the engine test button. A single test page with
will be printed. To print multiple test pages, hold down
the engine test
If the engine test prints ok then you have a formatter issue...if you have added memory or a network card try taking them out one at a time to see if the problem goes away. Otherwise the formatter will have to be replaced.