I have a HP Color LaserJet CP1515n here that refuses to print cyan.

When you try to print a document with blue in it, the page prints out red.

However when i print out a supplies page and diagnostics page, cyan prints out.

When i print a windows printer test page, the xp logo doesn't print the blue part of the logo; it comes out as a faded red colour.

I have tried the following:

changed the toner
upgraded firmware
reinstalled driver
used the HP Universal driver
tried printing using different programs
tried printing using usb and network interfaces
tried different computers
tried the cleaning function on the printer

does anyone have any ideas to what could be wrong with it?