ceci n'est pas un btree

As part of a nightly build process we are building an 8.0.1 database,
creating a schema, etc. Intermittently we are getting the error

ERROR: index "xyz" is not a btree

In the archives I found a post from Tom
http://archives.postgresql.org/pgsql-admin/2005-05/msg00103.php
<http://archives.postgresql.org/pgsql-admin/2005-05/msg00103.php> that
suggested this was a bad pg build or a flaky harddrive. I will look into
the hardware issue, but I was wondering in what way I could have screwed
up the build of postgres to get this kind of error? I see where the
error is being emitted in the _bt_getroot and _bt_gettrueroot methods,
but I don't what would be configure/build sensitive in there.

Incidentally, when I try to search the archives on "is not a btree", I
get all hits for btree, presumably because all of those other "little"
words in the phrase are stop-listed? Is there an escape sequence I can
use to get the search to work for only that whole phrase (I realize this
is probably basic google stuff, but I was born before the web....)

Thanks.

- DAP
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David Parker Tazz Networks (401) 709-5130