This can happen from folding the kite really fast & putting twists in the leading edge, or when you pump the LE up without laying the kite out nice & flat. Anyway its easy to fix.

What you need to do is pull the side of the bladder thats twisted out, or just the whole bladder if you not confident and follow the instructions available at the North website for putting in a bladder (its easy)....

http://www.northkites.com/index.cfm

Go to the downloads section a watch the video on it.
Also a tip is to get a friend to help for pulling out & putting back in the bladder.(get them to pull the string while you feed the bladder through) Use a bit of baby powder to help it slide into place & fold the badder up so it's easy to feed through & you know its all going in the right way.

Thanks for the tips.

I used to get this all the time. Put a heap of baby powder down there and that should help it slide around. When you pump up make sure the middle of the leading edge where you pump it up is straight. If you start with a kink there, when it gets hard and straightens the valve gets pulled in.