Lion - Macbook randomly wakes up from sleep when lid is closed
It is possible to determine what caused the system to wake
- Open Console (/Applications/Utilities/Console)
-
Set the search filter to 'wake'
You're looking for the latest entry that has something like this:
Wake reason = EC LID0(In the example above, opening the display clamshell caused the machine to be woken)
Here's a list of wake 'reasons' from OSXDaily
This should shed some light on what is waking the machine, then you can go from there.