IIS Worker Process stopped working and was closed

Greetings,
I've already posted this message on aspnet and aspnet.security newsgroups
but someone said it has to do with IIS, so Im posting it here.


I have an aspnet 1.1 application that works perfectly on Windows XP, Windows
2000 and Windows 2003.

When trying on Windows Vista (set application for aspnet 1.1 on IIS), the
application crashes Internet Explorer with the message:
"IIS Worker Process stopped working and was closed"

Doing some debug, I found that the errors is caused when accessing a method
from an external dll (win32).
I use dllimport to define the method, something like:

[DllImport("name.dll", CharSet=CharSet.Ansi, EntryPoint="functionname")]
public static extern string functionname (string SomeParameter);


I've searched a lot for a solution, and tried different aproaches, like
giving full access to dll file to everyone, impersonating, enabeling
unmanaged code debug, moving dll to system32 path, checking that the
application is with Full trust level on IIS, etc.

I know the problem is not the dll path, since aspnet is finding it (if I
remove the dll from bin folder, it throws an error of file not found).

The dll doesn't have any GUI or output. It just do some encryption.


I thought that it could be a problem with the dll on vista, but if I create
a winform application, the dll works fine, so the problem is aspnet related.


Doing new tests with a new aspnet application using Classic .NET AppPool and
DefaultAppPool gave the same results, so I think the problem is not related
to selected application pool.



Appreciate any help on this subject,

Nelson R.