Ok, I think alot of people here have had problems with minecraft, where the screen suddenly turns black while having render distance "far " on.A temporary fix is to set the render distance to "normal" but it ruins the view.
So I searched a little bit on google, read several topics about allocating more ram to minecraft. I tried it, but for me it didnt help at all. So I thought the problem maybe could be with java, so I updated it and still it didnt work on "far" distance without crashes. I located their website and noticed that they have a new beta version of java. I thought that could be cool to try. So I downloaded the beta (aka java 7), uninstalled java 6 and installed java 7. I started up minecraft and tada! I could run minecraft of "far" render distance without crashes now!
So if you want to try link here: http://download.java.net/jdk7/
This is beta, so it can have some bugs, but I havent encountered any. yet.