Something wrong with that?

Unfortunately, I'm guilty of this myself. I just get busy, and so on my list of priorities, someone I just started randomly messaging on myspace is obviously not as important as school/work/family, etc. Just try not to take it personally. Instead of messaging, you might try to just send a friend request, then if they add you, you can comment their page and say thanks for the add, and hopefully they will respond back with something. That way it's not so much a dialog that has to be answered promptly, but just a sporadic comment where you can get to know her a little more slowly and at a more comfortable pace.

You might want to try using a dating site like plentyoffish or okcupid.
I don't know about other girls, but I am very wary of talking to anyone on myspace if I don't know them.

Don't beat yourself up over this! You are doing nothing wrong. I'm on myspace and facebook as well so I understand what you are talking about. I have girls that I have known for years, grew up with, that act that way on there. People just get busy and don't get on for a period of time. Or they read your message and are too busy to type back at that time and it slips their mind later. It is not that they don't like you or you are unimportant; it's just they are tied up for the moment. As long as you are patient and keep the conversation like you say you are, then they will eventually come around. You can't push someone you just met, cause they don't know you. They have not invested any time into your relationship, so just give it time.