Multicolumn index corruption on 8.4 beta 2

Hi,

I pgdump'ed a 8.3.7 database and loaded the dump to a different server
running PostgreSQL 8.4 beta 2 (compiled from source) under Opensolaris.

One of the tables has about 6 million records, and a Btree index that
spans 3 columns.

I am having the problem that some queries are unable to find rows when
using the index.
When I force a sequential scan, by doing "set enable_indexscan=false;
set enable_bitmapscan=false;", the same queries work fine.

In addition, while running "vacuum full analyze" I got the following
error a couple times:

==
ERROR: failed to re-find parent key in index "pgb_idx" for deletion
target page 25470
===

Doing "reindex" or dropping and creating the index, makes the error go
away for a while.
However it does not solve the problem of the missing rows, making me
believe the index Postgresql generates is still corrupt.

According to memtest the memory of the server is fine, and according to
"zpool status" there are no disk or ZFS checksum errors.

Any idea how to solve or debug this issue?

Yours sincerely,

Floris Bos