> I have a IB_Query OnActiveChange event which simply does that

I suggest that OnActiveChange may be an inappropriate place for this
code. AfterOpen would probably be better, then again why not just
activate the necessary datasets together then you activate the first?

Your alternative is probably to setup an internal flag to stop your
OnActiveChange code from being called recursively...

if FInternalFlag = 0 then
try
Inc(FInternalFlag);
<do your stuff>
finally
Dec(FInternalFlag);
end;

> Does it help in something the information?

Some info from the CallStack may have been more help, but your
simplest solution is probably one of the above.

--
Geoff Worboys - TeamIBO
Telesis Computing