Unpredictable signal 11 crashes on Mac OS X

Hi,

We've been having a lot of problems with unpredicatable crashes with
7.3.4 on OS X Server (10.2.6 and 10.2.8 exhibit the same behaviour).
Having run with verbose logging for some time, we have not noticed any
real consistency in the types of queries which are causing the crash
recently. A few weeks ago we were noticing crashes most commonly when
processing queries with extremely large IN () lists (> 1000 entries)
but we have now removed most of these from the application and are
still seeing crashes. Some days we get none, some days they happen
every five minutes! Today we have connected to the backends with gdb to
get a bit more information and have seen the following problems:

Program received signal EXC_BAD_ACCESS, Could not access memory.
0x0012c284 in hash_search (hashp=0x0, keyPtr=0x1195b84,
action=3212837216, foundPtr=0x1195b80 "") at dynahash.c:512
512 {

Program received signal EXC_BAD_ACCESS, Could not access memory.
_copyRangeTblEntry (from=0x12836c0) at copyfuncs.c:1455
1455 {

Has anyone got any clues or suggestions? Looks like some kind of stack
corruption to me but I don't know what we can do to solve it. The
relevant background info is:

Hardware:
Apple Xserve (cluster node), 2 x 1GHz processors, 2GB RAM

Software:
Apple Computer, Inc. GCC version 1175, based on gcc version 3.1
20020420 (prerelease)
Darwin palin.egsgroup.com 6.8 Darwin Kernel Version 6.8: Wed Sep 10
15:20:55 PDT 2003; root:xnu/xnu-344.49.obj~2/RELEASE_PPC Power
Macintosh powerpc
PostgreSQL 7.3.4 built with: ./configure --with-includes=/sw/include/
--with-libraries=/sw/lib --prefix=/
Volumes/Palin-RAID-Array-1/pg/postgresql-7.3.4
Fink 0.13.2 distribution version 0.5.3.cvs (for readline)

Non-default postgresql.conf settings:
max_connections = 60
shared_buffers = 200 # min max_connections*2 or 16, 8KB each
sort_mem = 1024 # min 64, size in KB

Thanks in advance
Gareth Boden

eGovernment Solutions Limited
Baird House, 15-17 St Cross Street, London EC1N 8UW
t: 020 7539 2815
f: 020 7539 2829
www.egsgroup.com