HP 5550 printer--blank pages?

I have an old HP 5550 deskjet which I only use occasionally, mainly
for envelopes, but suddenly today, I noticed that while it goes thru
the motions of printing, nothing shows up on the page. I've cleaned
the cartridges numerous times, all the way thru "prime", and a printed
page comes out that I guess is correct (I don't do this regularly). I
can even print a test page (which shows only a horn's keys and a small
HP logo). Looks fine, and because the printing assistant shows the ink
levels on both cartridges as being full AND I get a test page, it
seems that there is not a problem with the cartridges or the nozzles.
However, it will NOT print out of Word 2003 or even notepad. As noted,
it acts like it's printing, the print head moves across the paper
normally, but literally nothing shows up. There has been no change in
my Office installation either.

I've tried reinstalling the printer several times, the drivers are all
up to date, all to no avail. It clearly THINKS it's printing fine, but
nothing shows up.

Any thoughts?

TIA

elaine