Application Access Violation or Hang After Applying SP4
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The information in this article applies to:

Microsoft Windows NT Server version 4.0
Microsoft Windows NT Workstation version 4.0
Microsoft Windows NT Server, Enterprise Edition version 4.0
Microsoft Windows 2000 Advanced Server
Microsoft Windows 2000 Datacenter Server
Microsoft Windows 2000 Professional
Microsoft Windows 2000 Server

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IMPORTANT: This article contains information about editing the registry. Before you edit the registry, make sure you understand how to restore it if a problem occurs. For information about how to do this, view the "Restoring the Registry" Help topic in Regedit.exe or the "Restoring a Registry Key" Help topic in Regedt32.exe.


SYMPTOMS
After applying Windows NT 4.0 Service Pack 4 (SP4) or Windows 2000, you encounter lockups or access violation (Dr. Watson) errors in an application that appeared to be working fine previously.

NOTE: You might encounter other symptoms or errors in an application that relate to the below-mentioned cause.



CAUSE
The application in question is errantly trying to access a block of memory that it had previously freed or deallocated. With Windows NT 4.0 Service Pack 3 (SP3) and earlier, such a reallocation is more likely to succeed, since the same memory location is more likely to still be available for reallocation. SP4 and later, however, introduces a change in the heap manager allocation patterns that can result in a failure of such a reallocation request. For more information on this change, please see the following article in the Microsoft Knowledge Base:

Q195008 Heap Manager Change in Service Pack 4



RESOLUTION
WARNING: Using Registry Editor incorrectly can cause serious problems that may require you to reinstall your operating system. Microsoft cannot guarantee that problems resulting from the incorrect use of Registry Editor can be solved. Use Registry Editor at your own risk.

For information about how to edit the registry, view the "Changing Keys and Values" Help topic in Registry Editor (Regedit.exe) or the "Add and Delete Information in the Registry" and "Edit Registry Data" Help topics in Regedt32.exe. Note that you should back up the registry before you edit it. If you are running Windows NT or Windows 2000, you should also update your Emergency Repair Disk (ERD).

To determine if the above-mentioned change is exposing a problem in the application in question, proceed with the following steps. If these steps result in the application generating fewer or no more such errors, contact the vendor of the application to inquire about an updated version of the application that resolves this problem.

NOTE: There are other conditions that can cause such errors or hangs that are not related to this change introduced in SP4 and Windows 2000. If the following workaround does not correct the problem, query on the error or condition you are encountering and the application name in the Microsoft Knowledge Base and/or check with your application vendor for more informat