When I close my laptop without shutting down, and then open it back up it won't come out of sleep. I held down the power button and tried to turn it on again but to no avail. I finally took the battery out for a few minutes and then tried starting up and it worked just fine. I haven't had any performance issues when the machine is on or when i restart or shutdown "properly", this problem only occurs when i close my laptop without powering down first. Any suggestions?