Hi Don,
When calling a native .dll from an ASP.NET application running under IIS you normally need to set the location of the .dll within your PATH in order for the .dll to be picked up correctly even if it is in the current folder with the application.
That is because when the web pages are loaded they are compiled and run from a temporary directory which means the .dll is no longer in the "current" folder.
Try setting the PATH in web.config or in your System environment variables and then rebooting to ensure that IIS picks it up.
Thanks.