DOCUMENT:Q150467  24-SEP-1996  [vbwin]
TITLE   :PRB: Modal Form Flickers When Exiting Form with DBGrid Control
PRODUCT :Microsoft Visual Basic for Windows
PROD/VER:4.00    | 4.00
OPER/SYS:WINDOWS | WINDOWS NT
KEYWORDS:kbprg kbprb

------------------------------------------------------------------------
The information in this article applies to:

 - Standard, Professional, and Enterprise Editions of Microsoft
   Visual Basic, 16-bit and 32-bit, for Windows, version 4.0
------------------------------------------------------------------------

SYMPTOMS
========

Under certain circumstances, unloading a form containing a DBGrid control
causes Visual Basic to hang and other open forms to flicker. After hiding
the third form of the program, the second form flickers or blinks. Under
the 16-bit edition of Visual Basic, an application error follows the
blinking, and displays the following error message:

   VB caused a general protection fault in module VB.EXE at 000b:000039f3.

CAUSE
=====

The problem is limited to the following combination of circumstances:

 - A project contains at least three forms with each form containing the
   DBGrid control.

 - The first form shows a second, modal form. The problem does not occur
   if the second form is not shown modally.

 - A single form creates two or more instances of the original form.

RESOLUTION
==========

There are two possible resolutions to the problem. Either solution prevents
the problem from occurring:

 - Do not show the second form as a modal form.

   - or -

 - In the Unload event of the third form, add the following line of
   code:

   Me.Enabled = False

STATUS
======

This behavior is by design.

MORE INFORMATION
================

Steps to Reproduce Problem
--------------------------

1. Create a Visual Basic project with three forms.

2. Add a Command button to Form1. Place the following code in the
   Click event of the Command button:

   Form2.Show 1

3. Add a Command button to Form2. Place the following code in the
   Click event of the Command button:

   Form3.Show 1

4. Add a DBGrid control to Form3. Run the project.

5. From Form1, click the Command button to show Form2. From Form2, click
   the Command button to show Form3. Close Form3.

Additional reference words: 4.00 vb4win vb4all
KBCategory: kbprg kbprb
KBSubcategory: PrgCtrlsStd


=============================================================================

THE INFORMATION PROVIDED IN THE MICROSOFT KNOWLEDGE BASE IS
PROVIDED "AS IS" WITHOUT WARRANTY OF ANY KIND.  MICROSOFT DISCLAIMS
ALL WARRANTIES, EITHER EXPRESS OR IMPLIED, INCLUDING THE WARRANTIES
OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE.  IN NO
EVENT SHALL MICROSOFT CORPORATION OR ITS SUPPLIERS BE LIABLE FOR
ANY DAMAGES WHATSOEVER INCLUDING DIRECT, INDIRECT, INCIDENTAL,
CONSEQUENTIAL, LOSS OF BUSINESS PROFITS OR SPECIAL DAMAGES, EVEN IF
MICROSOFT CORPORATION OR ITS SUPPLIERS HAVE BEEN ADVISED OF THE
POSSIBILITY OF SUCH DAMAGES.  SOME STATES DO NOT ALLOW THE EXCLUSION
OR LIMITATION OF LIABILITY FOR CONSEQUENTIAL OR INCIDENTAL DAMAGES
SO THE FOREGOING LIMITATION MAY NOT APPLY.

Copyright Microsoft Corporation 1996.