"out of balance" result on select from suspected index corruption

Hello,

PG:  8.2.7 (then upgraded to 8.2.9 to try and resolve with same result)
Linux 2.6.25

Our selects which have run normally for a very long time suddenly started:

- consuming all memory.
- crashing (oom) if the select was run directly.
- producing "out of balance" results in one of the column results if run
from within a function.

In an effort to resolve, I upgraded to 8.2.9, which yielded the same results.

VACUUM [full analyze] on the db or suspect table resulted in same as above.
Eventually, I tried reindexing the table, which also failed as above.

The workaround was to manually drop each index from the offending table,
then re-create them.

The weird "out of balance" message in one of the column results (ie,
instead of 'bob' as a result for that column, it would simply be "out of
balance").

Sorry I can't provide more detail since this happened yesterday as we're
preparing for the month-end billing run (and getting things back online
was critical).... :-(

Regards
Henry