page position (margins) shifted for epson C86 on FC5

I've just upgraded from Fedora Core 1
(kernel: 2.4.22-1.2199.5.legacy.nptl) to Fedora Core 5
on a new 64-bit machine (kernel: 2.6.16-1.2111_FC5 #1 SMP)
and upon configuring my Epson Stylus C86 printer, am
finding an annoying glitch:

Almost every time it prints a page the margins are
incorrect.  The image is shifted down by about
50 points and shifted right by about 8 points.
It is, alas, not a consistent error; very
occasionally the margins are correct.  This happens
for the redhat test page and for the TeX testpage,
and for other text pages I've printed, all of which
print correctly on my older (FC1) machine, with
identical printer configurations on both machines.

I've looked at the (~300 line) error logs on both
machines (in the /var/log/cups directory), obtained
by setting "LogLevel debug" in /etc/cups/cupsd.conf,
but can see no hints from those as to what might be
mis-behaving.

Does anyone have suggestions for what might be going
on, or what I might try to track down this glitch?

I'm at a loss for what to try next.  I don't know if
it's a cups problem, or a ghostscript problem or a
foomatic problem or a kernel problem.  It does not
seem likely to be a printer problem since everything
works like a charm on my old machine.

I can supply copies of the error logs or of the key
lines in my cupsd.conf files if those might be
helpful.

Any suggestions would be most appreciated.

        -- Peter

p.s. I also have an Epson Stylus C88 printer, which
behaves in exactly the same way as the C86 printer.