One more precision...

> - To fix the pb ( until the next slowdown ), all I found is to sweep the

db.

> It takes about 20 minutes, which is no more than the regular sweeping
> duration for this db.

Actually, I just noticed the db could cure itself without a sweep. I've been
playing all the afternoon with it issuing the guilty statements dozen of
times against various part of the table. And suddenly, speed went back to
normal.
Note that, between statement executions, fbserver.exe did not eat any CPU
power. It's really only during statement execution that "something" happens.

Regards.

--
Jerome