Canon BJC-50-Not Working With Gutenprint in OS X 10.6.8 Anymore

Had worked passably (slow and used too much ink but print quality was
OK) for most of the past seven years on a MacBook Pro originally running
OS X 10.4.11. Still worked when I upgraded to Snow Leopard and
Gutenprint 5.2.9. All of a sudden, however, it won't print in color.
When I try I get only a black-and-white image that's way too dark and
pictures that almost look like photo negatives.

Among the things I've tried are completely uninstalling and reinstalling
Gutenprint, resetting the printing system, trying both ColorSync and
Vendor Matching under Color Matching, changing Color Model between RGB,
CMYK, KCMY, Republican, Democrat, Indepenedent or whatever else is in
there. In short, I've played around with anything that looks like it
might help.

I've got several other printers that still work fine with OS X and the
BJC-50 works just as great as ever with Windows (95, Vista and 7) so my
guess is we're looking at a software problem such as a setting that
somehow got changed. Any ideas where to start?