Why did this girl suddenly stop talking to me?

No idea what went wrong, sorry! But it is pretty clear something happened and for whatever reason she doesn't want to see you again. Best thing you can do is accept her wishes, take some time to recover and move on.

If it's any help - my friend once did something like this to a guy after what he would have thought were a couple good dates- she said she had fun and the dates were nice but she kind of got caught up in the moment. Once she had a chance to think things over she realised she just wasn't feeling the chemistry, so she ended things. She told him that and when he kept contacting her after she'd made it clear she wasn't interested, she did cut off all contact. It could be something as simple as that - she had a nice date but upon reflection she wasn't feeling the chemistry she should have been during the kisses. It doesn't sound like you did anything wrong. My guess is you two simply aren't suited.

I agree with the other answer. A lot of times you meet someone, get caught up in the moment of meeting them, etc. Then you realize later on that perhaps you don't really want a relationship after all or there is no chemistry there that you thought would be there.

I was on a dating site for awhile and met a guy for lunch and I could tell by the end of the lunch I wouldn't want to date him. I felt badly about it, but at least I emailed him and told him that I decided I really wanted to be single for awhile longer. I didn't want to hurt his feelings but there were a lot of reasons I didn't want a relationship with him. Just the personality wasn't what I wanted.

I think it was really wrong of her to just stop talking to you and cut you off without a reason. That's pretty cruel. But...that's happened to me before with guys.

It could be a number of reasons and unless you find out what the reason(s) are you'll give yourself a headache trying to figure it out.

Female friends, work colleagues and acquaintances have all ignored me in the past and currently two work colleagues have started ignoring me in the last few weeks and I have no reason why they are but you know? That's not my problem, that's their problem and I couldn't care less. If someone has an issue with me then come and talk to me about it and I'll try my best to remedy the situation within reason. If someone wants to ignore me, that's fine, I'll back away, leave them alone and life goes on as usual.