BUG #1800: "unexpected chunk number" during pg_dump

The following bug has been logged online:

Bug reference:      1800
Logged by:          Aaron Harsh
Email address:      ajh@rentrak.com
PostgreSQL version: 7.4.6
Operating system:   RedHat ES release 3, x86_64
Description:        "unexpected chunk number" during pg_dump
Details:

Our regular pg_dump aborted this afternoon with this output:

pg_dump: ERROR:  unexpected chunk number 0 (expected 1) for toast value
4294879152
pg_dump: SQL command to dump the contents of table "dataset_cache" failed:
PQendcopy() failed.
pg_dump: Error message from server: ERROR:  unexpected chunk number 0
(expected 1) for toast value 4294879152
pg_dump: The command was: COPY public.dataset_cache (checksum, version_no,
bind_params, sql_statement, serialized_value, date_created) TO stdout;
pg_dump: *** aborted because of error

We saw the same message when we tried to cluster the effective table.  The
problem went away after truncating the table.

I've searched the pgsql-bugs archives and found reports of this problem, but
haven't seen a solution.  Is there a solution to keep this from happening in
the future? (Version upgrade maybe?)