pg_dump error

Hi,

What does this mean ?!? Is this a corrupt database, a bug or has the pg_dump
not enough memory ?
And ... how can i solve this problem ?

$ pg_dump login | gzip > login.dump.gz
pg_dump: ERROR: MemoryContextAlloc: invalid request size 4294967293
pg_dump: lost synchronization with server, resetting connection
pg_dump: SQL command to dump the contents of table "postcodereeks" failed:
PQendcopy() failed.
pg_dump: Error message from server: pg_dump: The command was: COPY
"postcodereeks" TO stdout;

$ psql -c 'COPY "postcodereeks" TO stdout;' login > /tmp/postcodereeks
ERROR: MemoryContextAlloc: invalid request size 4294967293
lost synchronization with server, resetting connection

Config:
Machine; dual PIII with 1 Gb memory
DB version: PG 7.2.1

postgres.conf:
<zip>
shared_buffers = 2048
sort_mem = 1024
<zip>

Regards,
Ferdinand