Thanks Hui,
SHMMAX was set to 0x2000000 in that .h file. So it looks as though the
system wasn't allowing anything to allocated more than 32 meg of shared
memory (as I found out with the -B option on the postmaster). I haven't
had a chance to go through re-building the kernel. Our IT guy here says
that it is a little involved on Red Hat so I'll hold off for a while
until I have the time.
-Tony