Severe SUBSELECT bug in 6.5 CVS

Using the very latest CVS I'm encountering a bug in SUBSELECTs.
This query returns 22 rows...

SELECT id,title FROM question;

This query returns 15 rows...

SELECT id,title FROM question WHERE question.id IN (SELECT webobject
FROM comment);

Therefore I would expect this query to return 7 rows. Instead it returns
none....

SELECT id,title FROM question WHERE question.id NOT IN (SELECT webobject
FROM comment);

I've tried it with a newly dumped and created database and it still
happens. However I can't get it to happen on a new and empty database
with simple data. In other words I can't come up with a simple test
case. All I can think to do therefore is put my data in a file for
download. It is 100k.

ftp://ftp.tech.com.au/pub/datadump.gz

As an aside, while creating this dump I tried to load it into another
database and drop a few tables to make it smaller. I then tried to dump
it again and got the following error...

dumpRules(): SELECT failed for table productv. Explanation from
backend: 'ERROR: cache lookup of attribute 1 in relation 1864370 failed

--
Chris Bitmead
mailto:chris(at)tech(dot)com(dot)au