Article ID: 193529
Article Last Modified on 11/5/2003
APPLIES TO
- Microsoft BackOffice Small Business Server 4.0
- Microsoft BackOffice Small Business Server 4.0a
This article was previously published under Q193529
SYMPTOMS
When a Microsoft Small Business Server client attempts to perform a modem sharing function, it may define the user as "user-mode programmer" and when opening a remote COM port to send an IOCTL #0, generate the following blue screen error message:
NOTE: The four parameters can vary according to the configuration of the system.
CAUSE
In the client's modem sharing driver code, there is a function dispatch table. It maps IOCTL requests (by their ID) to their handling functions. There is only a check for the upper limit of the IOCTL code but, in fact, the entry with ID 0 is invalid. Thus, sending an IOCTL with ID 0 causes an underflow in an array (for example, bad lookup) and a blue screen error message is generated.
RESOLUTION
To resolve this problem, obtain the latest service pack for Windows NT 4.0 or Windows NT Server 4.0, Terminal Server Edition. For additional information, click the following article number to view the article in the Microsoft Knowledge Base:
152734 How to Obtain the Latest Windows NT 4.0 Service Pack
Please note that this is a client-side issue and the fix must be applied on the Small Business Server client running on Microsoft Windows NT version 4.0.
Keywords: kbbug kbfix KB193529
