Strange behaviour after using ADOConnection to Access database


I am using Delphi 5 with MDAC 2.61 and Jet 4.0 SP3 for connecting an
Access database via ADO.

After I close the window using the ADOConnection(with ADOQuery) I have
problems in another window using the Trunc(Extended) function and only
BDE Paradox tables. I get an EInvalidOp Exeption although there is no
problem. If I open the second window again I have no problem.

Do I have to close the ADOConnection in a special way ?

Has anybody an idea ?