This article was previously published under Q193529
This article has been archived. It is offered "as is" and will no longer be updated.
When a Microsoft Small Business Server client attempts to perform a modem sharingfunction, it may define the user as "user-mode programmer" and when openinga remote COM port to send an IOCTL #0, generate the following blue screenerror message:
NOTE: The four parameters can vary according to the configuration of thesystem.
In the client's modem sharing driver code, there is a function dispatchtable. 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 anunderflow in an array (for example, bad lookup) and a blue screen errormessage is generated.
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 theMicrosoft 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 onthe Small Business Server client running on Microsoft Windows NT version 4.0.