Post the code you use to load the library. Provide the value for all variables used in that code.
Post the full path name of the library you are attempting to open. Also, do you know what other libraries your library depends on? The dependency walker can help you with that. (http://www.dependencywalker.com/) Are those libraries in the PATH? It could be that finding yoru library works just fine, but the loader fails because it can't find a library required by that library.
(Even I had a typo, I meant java.library.path, not jna.library.path! :^0 )