where the hell is my nx...?!

You can check your transaction log on nexon's website to see if someone bought something from the CS. Just log in, go to cash shop >> transaction log >> nexon cash usage. It'll show you what your NX has been spent on if they bought something in the Cash Shop... dunno if it shows MTS purchases because I don't buy from the MTS.

Also, sometimes lag causes your NX balance to come up 0. If that happens to me, I just exit and reenter the cash shop until the correct total comes up.

Hope this helps a bit. =/