Corrupted index file after restoring WAL on warm spare server

Recently I went through the steps to refresh the database (8.3.4) on my
development server (running Fedora Core 5 Linux),
making a tarball of the live database, then restoring it on the development
server, and running all the archived WAL files.

Everything worked fine as far as I can tell, I don't see any errors in any
of my logs.

Howevever, when I go to access one table, the index appears to be corrupted
because the record I get for one query doesn't match the record key I give.

The search works correctly on the live server.

Reindexing that table on the warm spare system fixes the problem.

I redid setting up the warm spare server a second time to see if it was a
one-time anomaly, but I have the exact same condition again.

What could be causing this? If this is a bug, what can I do to help track
it down?
--
Mike Nolan
htfoot(at)gmail(dot)com