pg_dump fails with memory exhausted error

I'm having a trouble with pg_dumpall.  I did a brief search of the
list archives and saw the same question asked at least two other times
in the last year, but never answered on the list.

pg_dump exits with the following error:
    FATAL 1:  Memory exhausted in AllocSetAlloc()
    PQendcopy: resetting connection
    SQL query to dump the contents of Table 'trace_hop_delay' did not
    execute correctly.  After we read all the table contents from the
    backend, PQendcopy() failed.  Explanation from backend: 'FATAL 1:
    Memory exhausted in AllocSetAlloc()
    '.
    The query was: 'COPY "trace_hop_delay" WITH OIDS TO stdout;
    '.
    pg_dump failed on iperf1, exiting

The table in question is the largest in the database -- about 19
million rows of 3 ints -- and gets dumped near the end of the run.  If
I execute 'COPY "trace_hop_delay" WITH OIDS TO stdout;' from psql, it
executes correctly.

Does anyone know what the cause of the problem is or how to work
around it?  Is there a postgresql bug list?

Jeremy