Mysterious server crashes

Hello!

Recently we have upgraded our debian system (sid),
which has since started crashing mysteriously.
We are still looking into that. It runs on 3ware RAID.
Postgres package is 8.4.8-2.

The database came back up apparently ok, except
for indexes. Running reindex produces this error on
one of the tables:

ERROR:  unexpected chunk number 1 (expected 0) for toast value 17539760 
in pg_toast_16992

Same with select.

I tried running reindex on toast table didn't help. Running:

select * from pg_toast.pg_toast_16992 where chunk_id = 17539760;

crashed postgres backend (and apparently the whole server).

Is there anything we can/should do to fix the problem, besides
restoring the whole database from backup?

Thanks!

Ziga