The problem may be due to SafeSleep, which is enabled by default on Macbooks and causes the laptop to write out the RAM to disk when put to sleep. Try turning off SafeSleep and see if that helps. My 2011 Macbook Pro started hanging occasionally when closing the lid after I upgraded to 8GB RAM, and turning off SafeSleep seems to have stopped it.
The problem may be due to SafeSleep, which is enabled by default on Macbooks and causes the laptop to write out the RAM to disk when put to sleep. Try turning off SafeSleep and see if that helps. My 2011 Macbook Pro started hanging occasionally when closing the lid after I upgraded to 8GB RAM, and turning off SafeSleep seems to have stopped it.
http://www.markc.me.uk/blog/files/OSXSafeSleep.html