Problems with gdb

Last night I was able to get a good stack trace out of some core files
to track down an issue with a corrupted index. Now I can't repeat that,
with either those core files or a new, unrelated coredump I've got.
Here's what I'm getting:

[root@pg4 coredumps]# gdb /usr/bin/postgres core.14888
GNU gdb Red Hat Linux (6.3.0.0-1.63rh)
Copyright 2004 Free Software Foundation, Inc.
GDB is free software, covered by the GNU General Public License, and you
are
welcome to change it and/or distribute copies of it under certain
conditions.
Type "show copying" to see the conditions.
There is absolutely no warranty for GDB.  Type "show warranty" for
details.
This GDB was configured as "x86_64-redhat-linux-gnu"...Using host
libthread_db l
ibrary "/lib64/tls/libthread_db.so.1".


warning: core file may not match specified executable file.
Core was generated by `postgres: iacm didit 216.187.113.78(51139) DROP
TAB'.
Program terminated with signal 11, Segmentation fault.

warning: svr4_current_sos: Can't read pathname for load map:
Input/output error

Reading symbols from /lib64/libpam.so.0...done.
Loaded symbols for /lib64/libpam.so.0
Reading symbols from /lib64/libssl.so.4...done.
Loaded symbols for /lib64/libssl.so.4
Reading symbols from /lib64/libcrypto.so.4...done.
Loaded symbols for /lib64/libcrypto.so.4
Reading symbols from /usr/lib64/libkrb5.so.3...done.
Loaded symbols for /usr/lib64/libkrb5.so.3
Reading symbols from /usr/lib64/libz.so.1...done.
Loaded symbols for /usr/lib64/libz.so.1
Reading symbols from /usr/lib64/libreadline.so.4...done.
Loaded symbols for /usr/lib64/libreadline.so.4
Reading symbols from /lib64/libtermcap.so.2...done.
Loaded symbols for /lib64/libtermcap.so.2
Reading symbols from /lib64/libcrypt.so.1...done.
Loaded symbols for /lib64/libcrypt.so.1
Reading symbols from /lib64/libresolv.so.2...done.
Loaded symbols for /lib64/libresolv.so.2
Reading symbols from /lib64/libnsl.so.1...done.
Loaded symbols for /lib64/libnsl.so.1
Reading symbols from /lib64/libdl.so.2...done.
Loaded symbols for /lib64/libdl.so.2
Reading symbols from /lib64/tls/libm.so.6...done.
Loaded symbols for /lib64/tls/libm.so.6
Reading symbols from /lib64/tls/libc.so.6...done.
Loaded symbols for /lib64/tls/libc.so.6
Reading symbols from /lib64/libcom_err.so.2...done.
Loaded symbols for /lib64/libcom_err.so.2
Reading symbols from /lib64/libaudit.so.0...done.
Loaded symbols for /lib64/libaudit.so.0
Reading symbols from /usr/lib64/libgssapi_krb5.so.2...done.
Loaded symbols for /usr/lib64/libgssapi_krb5.so.2
Reading symbols from /usr/lib64/libk5crypto.so.3...done.
Loaded symbols for /usr/lib64/libk5crypto.so.3
Reading symbols from /lib64/libnss_files.so.2...done.
Loaded symbols for /lib64/libnss_files.so.2
#0  0x0000002a9613cd20 in ?? ()
(gdb) bt
#0  0x0000002a9613cd20 in ?? ()
#1  0x0000002a9610f8cc in ?? ()
#2  0x0000000000852048 in ?? ()
#3  0x00000000005d6fcc in DirectFunctionCall1 (func=0x7fbfffd9b0,
arg1=Variable
"arg1" is not available.
)   at fmgr.c:882
#4  0x0000000000020000 in ?? ()
#5  0x0000000032d002cf in ?? ()
#6  0x0000000032cf32fd in ?? ()
#7  0x0000002ab8fe8380 in ?? ()
#8  0x0000002ab9053d00 in ?? ()
#9  0x0000000000000000 in ?? ()
(gdb)

Note that there is a /usr/lib/debug/usr/bin/postgres.debug, but
specifying that just gets me
warning: core file may not match specified executable file.
-- 
Jim C. Nasby, Sr. Engineering Consultant      jnasby@pervasive.com
Pervasive Software      http://pervasive.com    work: 512-231-6117
vcard: http://jim.nasby.net/pervasive.vcf       cell: 512-569-9461