I had the same issue.
What happened to me is I had to move around my files a bit.
Just kinda messed with it a bit till it allowed me to open newgen, when I DID open newgen, it looked like reg Blizz editor, cause everything "special" about it was turned off. JassHelper, USMWE, etc., all turned off.
Make sure you have the lists at the top. And turn them on if you do. Then restart it, and it'll work.
It annoyed the living crap out of me for a while.
Mind you, I haven't updated NewGen in a few years, lol.