I’ve been finding that my Mac has a chance to hang when I wake it up from sleep mode. It doesn’t happen often, but when it does, it’s really irritating.
It turns out the proble might have to do with a Bluetooth mouse paired with the computer. The default Mac OS X configuration allows Bluetooth devices to wake up the computer from sleep. Once I disable it (System Preferences, Keyboard & Mouse, Bluetooth), the problem seems to not happen anymore.
If you’re experiencing similar problems, give this a try!