Does anyone know how to correctly implement multi-threading on the NXT visual programming environment?
Yes, lots of people know how to implement multi-threading on the NXT visual programming environment.
Unless you are more specific, though, you aren't going to find out what's wrong with your particular problem. There are lots of gotchas, though.
For instance, if you have two threads inside a loop, the loop will not loop until BOTH threads complete.
There are many others - too many to enumerate here - so start debugging your program piece by piece, and post examples of your 'code' (screenshots?) and then describe what it's doing, and what you want it to do.