Today I turn on my MacBook Pro and it has probably frozen about 8 times for about 30 seconds each time. Any ideas why that could be? Also, i'm not sure if this is since snow leopard, I don't think it is, but every time I sleep my MBP or restart it my default sound output is switched from my external speakers to the built in LED display ones... why?! Also, my LED display, if I dim the brightness it hums like an overhead power line if you know the sound I mean? Any help appreciated.