bkQuery in D4 demos

Hi,

has anyone tested the demo bkquery shipped with D4 in the demos
directory?

Of course I did and after playing around for a while I found some
strange things:
Starting two queries - one of it takes only a few seconds and the other
one up to some minutes.

When starting the "big" query first followed immediately by the small
one, the small one waits for the first query!!! Very strange - since I
thought they are executed each in its own thread the same time?

Any ideas, hints, comments?

Michael