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Q269618: BUG: GPF May Occur When ComboBox Control Set on Band of CoolBar

Article: Q269618
Product(s): Microsoft Visual Basic for Windows
Version(s): 6.0
Operating System(s): 
Keyword(s): kbVBp600 kbOSWin95 kbOSWin98 kbGrpDSVB kbDSupport kbVS600sp5fix
Last Modified: 04-FEB-2002

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The information in this article applies to:

- Microsoft Visual Basic Professional Edition for Windows, version 6.0, used with:
   - the operating system: Microsoft Windows 95 
   - the operating system: Microsoft Windows 98 
   - the operating system: Microsoft Windows NT 
   - the operating system: Microsoft Windows 2000 
   - the operating system: Microsoft Windows XP 
- Microsoft Visual Basic Enterprise Edition for Windows, version 6.0, used with:
   - the operating system: Microsoft Windows 95 
   - the operating system: Microsoft Windows 98 
   - the operating system: Microsoft Windows NT 
   - the operating system: Microsoft Windows 2000 
   - the operating system: Microsoft Windows XP 
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SYMPTOMS
========

If you have a Visual Basic application with a ComboBox control set on a band of
the CoolBar control, it works as expected in versions of Visual Basic earlier
than Microsoft Visual Studio 6.0 Service Pack 4 (SP4). However, if you are using
SP4, the application may stop responding (crash) when the form that hosts the
CoolBar control closes. The crash only occurs on systems that are running on
Windows 98 or Windows 95.

CAUSE
=====

This behavior occurs because the controls set on the band of CoolBar are not
cleared at the correct time.

RESOLUTION
==========

To work around the problem, add the following line of code to the
Form_QueryUnload event handler:

  CoolBarName.Bands.Clear

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article.

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

Steps to Reproduce Behavior
---------------------------

1. Create a Standard EXE project with Visual Basic from Visual Studio 6.0 SP4 in
  Windows 98. Form1 is created by default.

2. On the Components dialog box, press the CTRL+T keys, select Microsoft Windows
  Common Controls-3 6.0 (Sp4), and then click OK.

3. Add a CoolBar control to Form1. Use the default settings.

4. Add a ComboBox control inside one of the bands of the CoolBar control.

5. Save the project and press the F5 key to run the application. Click the X in
  the upper-right corner of the form to close the form, and note that an error
  message similar to the following appears:

  Filename caused a general protection fault in module USER.EXE at
  0004:00000499.

  This program has performed an illegal operation and will be shut down. If the
  problem persists, contact the program vendor.

The Filename is the name of your project.

6. Re-open the project inside the Visual Basic integrated development
  environment (IDE). Sometimes Windows crashes when Visual Basic is re-opened,
  and you may need to restart your computer. You may also see a "resource is
  low" message box indicating that you need to shut down other applications or
  drivers running in the background.

7. Add the following code to Form1:

  

  Private Sub Form_QueryUnload(Cancel As Integer, UnloadMode As Integer)
      CoolBar1.Bands.Clear
  End Sub

8. Save the project and press F5 to run the application. Click the X in the
  upper-right corner of the form to close the form, and note that the project
  works fine.

  NOTE: If you click the End button in the Visual Basic IDE to end the
  application, note that you continue to see the problem because the
  Form_QueryUnload event handler does not have a chance to run. Therefore, do
  not end your application by using the End button in the IDE. To work around
  this problem, you can replace the SP4 version of the Comct332.ocx file in the
  system directory with the Visual Studio 6.0 Service Pack 3 version. You still
  need to implement the workaround mentioned in last step at the same time.

REFERENCES
==========

For additional information, click the article numbers below to view the articles
in the Microsoft Knowledge Base:

  Q189632 BUG: Error in CoolBar Event Can Cause Hanging or Exception

  Q189914 BUG: Wrapped CoolBar Control May GPF Client EXE Program

  Q257630 FIX: Exception Error Closing an Application Containing a CoolBar
  Control

Additional query words: Comct332 gpf halts halt

======================================================================
Keywords          : kbVBp600 kbOSWin95 kbOSWin98 kbGrpDSVB kbDSupport kbVS600sp5fix 
Technology        : kbVBSearch kbAudDeveloper kbZNotKeyword6 kbZNotKeyword2
Version           : :6.0
Issue type        : kbbug
Solution Type     : kbfix

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