Whenever I open minercaft, I sign in, "loading" pops up, and then the minecraft tab goes black... I can still exit, though.

You probably just have to update (or downgrade) your lwjgl files. Here is a link: http://www.minecraftwiki.net/wiki/Tutorials/Update_LWJGL.

Please provide more information like operating system, java version, graphics card type.

We are having the same issue. Window Vista machine with Mincraft 1.4.4. The log in comes up, we log in, the screen resizes o fullscreen, and then goes black. The only thing we can do is close out with task manager. We tried redownloading the game, but that did not work. What else can we try????

Since the problem, I had my amazing friend come I've, and she managed to solve this issue. What she did, was go to .minecraft, and then she deleted jar. When we tried to go back on minecraft, it automatically downloaded the new jar, and I could play minecraft normally again.

Look at MC-1106, there is a hint regarding fullscreen. Does that fix your issue ?