"Object reference not set to an instance of an object"

[Bob Cannistraci]

A three-tier user authentication system was running without a problem for almost a year and now is suddenly dysfunctional. We don't know of any changes to any of the servers. It's quite maddening. The details:

1) We know the COM+ app is instanced on the COM+ server (Win 2000). The component graphic spins when CreateObject is called.

2) The proxy is installed on an IIS server (Win 2000) with delivers the interface, written in ASP, to the client PC.

3) These are the error messages displayed when a method of DAMS is called:

----------------------------------------------------

Object reference not set to an instance of an object.
Description: An unhandled exception occurred during the execution of the current web request. Please review the stack trace for more information about the error and where it originated in the code.

Exception Details: System.NullReferenceException: Object reference not set to an instance of an object.

Source Error:

Line 116:
Line 117:Dim MyContextClass as Object = Server.CreateObject("DAMS.Context")
Line 118:Dim MyContextArray as System.Array = MyContextClass.list <<< THIS LINE FAILS
Line 119:Dim MyCounter as Integer
Line 120:Dim MySiteID, MySiteName as String

Source File: C:\IntranetLoginService\login.aspx Line: 118

Stack Trace:

[NullReferenceException: Object reference not set to an instance of an object.]
Microsoft.VisualBasic.CompilerServices.LateBinding .LateGet(Object o, Type objType, String name, Object[] args, String[] paramnames, Boolean[] CopyBack) +899
ASP.Login_aspx.__Render__control1(HtmlTextWriter __output, Control parameterContainer) in C:\IntranetLoginService\login.aspx:118
System.Web.UI.Control.RenderChildren(HtmlTextWrite r writer) +27
System.Web.UI.Control.Render(HtmlTextWriter writer) +7
System.Web.UI.Control.RenderControl(HtmlTextWriter writer) +243
System.Web.UI.Page.ProcessRequestMain() +1929

-----------------------------------------------------

4) Moving the COM+ app and ASP script to other servers does not solve the probelm.

5) When the app is directly called from a Win32 client there is no problem.

6) Finally, all servers are patched and up to date.

The NullReferenceException is baffling and the stack trace is not helpful in determining what the problem can be.

Any advice you can give will be appreciated. We need this problem debugged ASAP. Please let me know if you need more information.

Bob