I tried to play 1.5.2 because there is a working mcp for that version.

But when I hit "Play" In the launcher, it disappears (As I set it to do so)
and opens the client, it stays black for 2-5 seconds, and then crashes!

I don't know what could be causing it, only the client output logs generate in my minecraft1.5.2 folder. And it works just fine with 1.6.2.