To reproduce:

Click on play.

splash screen displays mojang logo then hangs

Development console shows no updates after:

Client> [09:03:21] [Client thread/INFO]: LWJGL Version: 2.9.0
Client> [09:03:22] [Client thread/INFO]: Reloading ResourceManager: Default
Client>
Client> Starting up SoundSystem...
Client> Initializing LWJGL OpenAL
Client> (The LWJGL binding of OpenAL. For more information, see http://www.lwjgl.org)
Client> OpenAL initialized.
Client>

Once it finally loads it shows:
Client> [09:04:43] [Client thread/INFO]: Created: 512x256 textures/blocks-atlas
Client> [09:04:44] [Client thread/INFO]: Created: 256x256 textures/items-atlas

TAKE NOTE OF TIME TAKEN!

Clicking on splash screen before it's done loading shows the status "Not responding" in the title bar. and white out the logo that's displayed.

Clicking Exit after above crashes the game