pg_dump crash

Hi, I have just received this crash on pg_dump:

PQgetvalue: ERROR! tuple number 0 is out of range 0..-1
Segmentation fault

it is 7.0.2 and about 130MB database which worked for me for more than a
year (it works as my 'local devel version' of a production system).

What can be the cause of this? I have been messing arround with indexes
just before the error. I wanted to drop some unused indexes and improve
some of my selects with multicolumn ones.
I tend to do drop indexes/vacuum analyze/restore indexes every day.
When I started my 'drop index/vacuum/reindex' script: BANG!
I do:

pg_dump -c -s database > schema.sql
grep -i "drop\ *index" schema.sql > ix_drop.sql
grep -i "create\ *unique\ *index" schema.sql > ix_recreate.sql
grep -i "create\ *index" schema.sql >> ix_recreate.sql
psql database < ix_drop.sql
vacuumdb -v -z database
psql database < ix_recreate.sql

in bash script. Despites its primitiveness it worked for a few months
flawlessly (I run it from cron on my production system nightly).

With the vacuum it crashed on a primary index of one
of the tables (the biggest one), but dropping/recreating the index fixed
the problem. Unfortunately it didn't serve the purpose for the
pg_dump...

pg_dump refuses working with any parameters (dumping data/schema,
selected tables, anything :-(

thanks in advance for any hint.

--
Marek Pętlicki <marpet(at)buy(dot)pl>