Glitching out Of Game Issue

I think this is a bug but it could be terribly wrong. Every thing is fine when i load Minecraft. I get into it. I see the title screen and then get tot the screen where it says multi-player and things like that. I go into multi-player and connect to any server. It lasts for about 2 seconds and then the whole screen justs goes wierd. The minecraft just goes white and then it says that minecraft has encountered a fatal error. I then tried deleting it and redownloading it many times but it doesn't work. Please help