DLL HELL

I have a 64 bit COM DLL that generates unlocking codes for a client.  I cannot edit this DLL.  It works SOMETIMES.

[DllImport(@"codegen64.dll")]
 public static extern string CreateCode2(
  int level,
  string name,
  string encrypt_template,
  Int64 hardwareID,
  int otherinfo1,
  int otherinfo2,
  int otherinfo3,
  int otherinfo4,
  int otherinfo5
  );

There is the page global DLLImport function... and when I try to use it...

try
  {
    unlockingcode = CreateCode2(1, regname, encrypt_template, lfp, 0, 0, 0, 0, 0);
  }
  catch (Exception ex)
  {
    unlockingcode = "";
  }

I get this pop-up dialog on my IIS server...

[Window Title]
Visual Studio Just-In-Time Debugger

[Main Instruction]
An unhandled win32 exception occurred in w3wp.exe [11016].

The Just-In-Time debugger was launched without necessary security permissions. To debug this process, the Just-In-Time debugger must be run as an Administrator. Would you like to debug this process?

[^] Hide process details  [Yes, debug w3wp.exe] [No, cancel debugging]

[Expanded Information]
Process Name: w3wp.exe
User Name: NETWORK SERVICE

Trying to invoke the debugger gives...

NOTE: I have enclosed the call to the DLL in a TRY block and it still fails, killing my WHOLE WEBSITE.
There MUST be a way to load, use, and unload a single DLL in a web page SAFELY, so that I don't get these HORIBLE crashes.

I have a feeling that the DLL is failing to unload, as it seems to work once, then fail until I restart the app pool and web site.
BUT I don't really know because I CANT DEBUG THE PROBLEM.
Sorry for the yelling, but this is like the ninth time I have told the client this is fixed, only to have it recur EVERY TIME a client orders from the web site!
Oh, it should be noted that I have NEVER installed Visual Studio on this web server.
Also, it's IIS8
.NET framework 4
Windows Server Essentials 2012....

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Bryan Valencia is a contributing editor and founder of Visual Studio Journey.  He owns and operates Software Services, a web design and hosting company in Manteca, California.