Strange CUPS behavior

[Jeff Vian]

Hopefully someone will be able to assist with this problem with
printing.

I have a machine with FC2, and cups is configured with 2 printers.
One, a laserjet 4plus is on the parallel port
the second, Canon S820 is on a usb port.

With cups I have set up the printers and can print test pages with no
problems.
>From the command line I can use "lpr -Pprinter <file>" and it prints
fine.
>From some apps (I have tested with evolution and OOo) it prints with no
problem toany of the printers.

The real problem is that other apps (I tried the GIMP) it will print
nothing.
I open an image file, tell it to print, select the printer, and go.
When I check the job status I see it "processing", then later it shows
as "completed" but nothing goes to the printer.

The only common thread I see is that the jobs that fail show in the
completed job list as coming from <stdin>.  All the jobs that complete
show a filename or source. 

Is this a problem with the GIMP (possibly) or something else?

The system is fully updated with all installed packages at the latest
using yum nightly. All packages seem to be intact. No errors reported
anywhere, just that the GIMP (and maybe others) refuse to actually
print.

Any pointers will be appreciated.

Thanks
Jeff