> on several PC following code is really slow:
>
> IB_Query.First;
> while NOT IB_Query.EOF do
> IB_Query.next;
> end;
>

...

> I found out, if I start the loop (via ButtonClick) and move the mouse outside
> the main window, the performance is nomal! Only if the mouse cursor is inside
> the window, performance is slow...

Does it help using DisableControls? I.e.:

try
IB_Query.DisableControls;
IB_Query.First;
while NOT IB_Query.EOF do
begin
IB_Query.next;
end;
finally
IB_Query.EnableControls;
end;

HTH,
Set