I’m having trouble landing the whip in Cheese Nips consistantly. Can anyone help?
Its not really a whip. You simply guide the slack into the gap 
But whenever I try, my string twists up. I just changed the string yesterday, too. What’s up with that?
Your string tension is messed up. Make sure you have neutral tension
slack into the gaps
Heres some tutorials to help you adjust your string tension.
http://www.youtube.com/watch?v=VJJwHP1AXYQ
Hope those help. and another one is this:
Do a split bottom mount, drop the string off your non-throw hand so all 3 strings are hanging from your throwhand index finger. Grab the middle string with your non throwhand and pull. It should spin around really fast. If your right handed this will loosen and if your left handed it will tighten…i think. It might be the other way around 
That was not helpful. If you want to post, please post more helpful posts. It also helps to read the posts ABOVE you before posting, so you don’t post what has already been said. Quanlity, not quantity.
Back on topic. My favourite way to stop the twisting is http://www.youtube.com/watch?v=PlQfcll1PLQ