If a girl stops texting you, there are a few things that could be going on. Perhaps she's busy, or another problem is going on.
I know that with cell phones, they can be touchy. Maybe she just had something go wrong with the phone and she hasn't been able to say anything yet.
Another idea is that she's just trying to avoid talking to you for some reason. Maybe it's because she no longer likes you, or you said something that was weird to her.
I mean, the only thing you can do right now is just wait. If you keep texting when someone isn't responding, they may end up getting a little annoyed at it. If she wants to talk, she will eventually.
Here are a couple of links to relationship texting advice:
1 - http://www.long-distance-lover.com/7-golden-rules-of-texting/
2 - http://www.divinecaroline.com/love-sex/ten-texting-no-nos-dating-and-relationships