Freezes and crashes on main menu

Whenever the game gets to the main menu, I have to wait at least a minute for it to stop freezing and stuttering for it to work properly. If I don't wait, there's a strong possibility that the game, or even my computer, will just crash. This has been a problem since 1.4, and I figured it would get fixed if I just gave it some time, but apparently not. I just had to hard-reset my computer because Minecraft was lagging so badly, that I couldn't even move my pointer. I know my computer isn't amazing, but 2.4 GHz dual core should be able to handle this well enough. I would appreciate it if someone would look into this. Thanks.