Segmentation fault while COPY in 7.3

Help!
Backend crashes on any COPY command I issue:
PostgreSQL is 7.3 release, is compiled from sources.
The message I get is:

apb=# COPY maras2.mrk_yyn (bsvr_no, yyn_tur, yyn_no, yyn_syf, yyn_trh) TO
stdout;
server closed the connection unexpectedly
This probably means the server terminated abnormally
before or while processing the request.
The connection to the server was lost. Attempting reset: Failed.
!#

The output of strace on backend is following:

# strace -p 18883
recv(7, "QCOPY maras2.mrk_yyn (bsvr_no, y"..., 8192, 0) = 77
gettimeofday({1038713111, 629131}, NULL) = 0
_llseek(11, 0, [0], SEEK_SET) = 0
read(11, "\0\0\0\0\20\0\0\0\1\0\0\0\24\0\360\37\360\37\1 b1\5\0\1"..., 8192)
= 8192
read(11, "\0\0\0\0x#\375\"\20\0\0\0008\0h\35\360\37\1 \370\235\220"...,
8192) = 8192
_llseek(12, 0, [0], SEEK_SET) = 0
read(12, "\0\0\0\0\0#\375\"\20\0\0\0008\0(at)\34\0 \1 \200\237\0\1\0"..., 8192)
= 8192
_llseek(21, 40960, [40960], SEEK_SET) = 0
read(21, "\0\0\0\0\4\251\3#\20\0\0\0004\4p\17\360\37\1 \340\237 "..., 8192)
= 8192
_llseek(22, 106496, [106496], SEEK_SET) = 0
read(22, "\0\0\0\0(\326\377\"\20\0\0\0\10\1\200\1\0 \1 \200\237\0"..., 8192)
= 8192
read(17, "\0\0\0\0\20\0\0\0\1\0\0\0\360\0\20\1\0 \1 p\237 \1\340"..., 8192)
= 8192
open("/data/pgsql/base/2015749/2015757", O_RDWR|O_LARGEFILE) = 39
_llseek(39, 0, [20037632], SEEK_END) = 0
_llseek(39, 0, [0], SEEK_SET) = 0
read(39, "\0\0\0\0\270\7\4#\20\0\0\0\300\1\350\1\0 \1 \270\237\216"...,
8192) = 8192
--- SIGSEGV (Segmentation fault) ---
+++ killed by SIGSEGV +++
#

I have recompiled postgres with debug information enabled, run gdb, attached
to backend process
and caught SIGSEGV as following:

(gdb) continue
Continuing.

Program received signal SIGSEGV, Segmentation fault.
0x081697bf in pfree (pointer=0x828a7b0) at mcxt.c:480
480 (*header->context->methods->free_p) (header->context,
pointer);
(gdb)

The output of bt is:

(gdb) bt
#0 0x081697bf in pfree (pointer=0x828a7b0) at mcxt.c:480
#1 0x080b37be in CopyTo (rel=0x402be088, attnumlist=0x828a3f8, binary=0
'\0', oids=0 '\0',
fp=0x0, delim=0x81c2a57 "\t", null_print=0x81b2c22 "\\N") at copy.c:671
#2 0x080b32f6 in DoCopy (stmt=0x827b398) at copy.c:491
#3 0x08118a6a in pg_exec_query_string (query_string=0x827af48, dest=Remote,
parse_context=0x8245378) at postgres.c:789
#4 0x08119b89 in PostgresMain (argc=4, argv=0xbfffd2a0, username=0x8240a81
"postgres")
at postgres.c:2016
#5 0x08101d7c in DoBackend (port=0x8240950) at postmaster.c:2293
#6 0x081016c2 in BackendStartup (port=0x8240950) at postmaster.c:1915
#7 0x08100875 in ServerLoop () at postmaster.c:1000
#8 0x08100326 in PostmasterMain (argc=1, argv=0x82270c0) at
postmaster.c:779
#9 0x080debab in main (argc=1, argv=0xbfffdc34) at main.c:210
#10 0x42017589 in __libc_start_main () from /lib/i686/libc.so.6
(gdb)

Thanks in advance,
Nic