Did you try changing the color cartridge, I know you say it's nearly full but if somehow it got clogged up through lack of use or whatever then it would not print anything out. If your test page came out in grayscale that is an indication that the color needs replacing if you had all your settings on color, or if the test page printed out the black stuff in black/gray and the color stuff was nonexistent.
Good luck, come in to the copy center if you need immediate help.
Cheers,
micki
