The DLL will soon be officially released.
I think I did some more fixes, and there was one which was very buggy.
But I don't know anymore which one I posted here.
If you can wait a bit there will be a new version released which worked for everybody up to now.
Maybe you're the exception to the statistics - then I'll have to check further
About your code:
wiimote_getdevices() does not return NULL but 0. But I'm pretty sure this is not the problem. As far as I remember Lite-C defines NULL to 0.
Edit:
Here is a console version built this month.
It should also detect the guitar hero guitar properly.
http://www.firoball.de/upload/ackwii_console.exePlease tell me what it reports on your system.