PRB: Modal Form Flickers When Exiting Form with DBGrid Control (150467)

The information in this article applies to:

Microsoft Visual Basic Standard Edition, 32-bit, for Windows 4.0
Microsoft Visual Basic Professional Edition, 16-bit, for Windows 4.0
Microsoft Visual Basic Professional Edition, 32-bit, for Windows 4.0
Microsoft Visual Basic Enterprise Edition, 16-bit, for Windows 4.0
Microsoft Visual Basic Enterprise Edition, 32-bit, for Windows 4.0

This article was previously published under Q150467

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

Create a Visual Basic project with three forms.
Add a Command button to Form1. Place the following code in the Click event of the Command button:
```
   Form2.Show 1
						
```
Add a Command button to Form2. Place the following code in the Click event of the Command button:
```
   Form3.Show 1
						
```
Add a DBGrid control to Form3. Run the project.
From Form1, click the Command button to show Form2. From Form2, click the Command button to show Form3. Close Form3.

Modification Type:	Minor	Last Reviewed:	7/15/2004
Keywords:	kbprb KB150467