Java crashed and now Minecraft won't load after the Mojang logo

When I was in the middle of the game, Java crashed so I logged off, uninstalled and reinstalled Java (because I have no idea how to fix it), and relogged, expecting it to load fine, however when the Mojang logo came up the Minecraft tab went black. At the bottom of my screen an extra tab labelled "Minecraft Minecraft..." appears and unless I press the start button on my keyboard, I can't do anything and when I do the window disappears. I've attempted to play on the downloaded version and the browser version and both get stuck after the Mojang logo (except on the browser the game turns white not black).

How to get there :
1. Open Minecraft (in browser or download)
2. Log in
3. Wait for the Mojang logo to appear
4. It turns black/white