Update problems

Please help!

I am currently running minecraft on the mac in version 1.3.2 and looking to update to 1.4.7 but every time it reaches 17% it says there is an 'error occurred (4)' and then the file location of minecraft.

I've already tried wiping the game and red ownloading but the problem remains.

Is there anyone out there that will actually help a keen player?