Ann!

I did a restore of my failing production base on WI 1.5.2.4731, and
the problem seems to have disappeared. I now get the correct results.

I am, however, very interested in seeing a working version of your
test case showing the problem you discovered with foreign keys.

My production views (well - the tables they are based on anyways) do
have foreign keys, which does not seem to bother FB 1.5.2.