We have developed the application which import and export some data in QuickBooks using QODBC driver.

But QuickBooks cannot be closed after the using of QODBC driver.

Our application was developed using Delphi7 and ADO controls.
QuickBooks version is “QuickBooks Enterprise 7.0”
QODBC driver version is “QODBC Desktop Read Write 2007 Version 7.00.00.214” (Licensed)
QODBC driver is configured to use the company file that’s now opened in QuickBooks

I have created the simple application using Delphi (ADOConnection and ADOQuery on the form). The same behavior is reproduced with that application. I do the following: open connection (ADOConnection.Connected:=True), open query (ADOQuery.Open), close query (ADOQuery.Close), close connection (ADOConnection.Connected:=False), !!! wait several minutes!!!, do the same things (open connection and query, close query and connection), after that close test application and try to close QuickBooks. As the result we cannot close QuickBooks. If we do not do !!! wait several minutes!!! then QuickBooks closes after closing the test application.

Try closing the Delphi7 test application and check the behaviour using VB Demo. If you sent an invalid query to QODBC, it's also possible to leave a broken connection in memory that won't let you close QuickBooks. See: I'm getting the error message "Cannot close company file" for more information. 

See also: Ado Item Query returns EOF in Delphi when wrong Cursor type is used