Car Wouldn't start...easy fix luckily!

[wullaby]

So my wife goes out this morning and she says X5 won't start, she needs to get to work and so do I, So I take her down the street to her parents and she borrows her dad 530i for the day, she calls to tell me how much nicer a ride it is! Anyways off to work I go thinking crap what could this be now. I just changed the starter a few months ago, battery is 2 years old, gas tank is half full, it was 0 degrees out but its in the garage. I did some research and people says it could be the key is faulty, ignition switch, or trans not in gear. So I come home from work put it in neutral and starts right up! put it back in park and start again no problem! I hope thats all it is that my wife didn't engage it fully into P the nite before...anyways it was an easy fix luckily! If for some reason this repeats again I heard it could be the Neutral SW going bad?