Applications won't open, F-Keys not responding, power button not responding, Apple menu not responding

Sometimes, and I still haven't found a common cause, I will find that I am unable to open any new programs. If I click a program either in the dock or in the Applications folder, the programs icon will bounce on the dock as if it is opening, and then, a few seconds later, will either simply disappear as if it was closed or stop bouncing. When this happens, I also lose any ability to use any of the F-keys. Additionally, the only way to fix the problem I've found is a reboot. However, the physical power button does nothing, and neither does anything within the Apple menu at the top left. This means the only option is to hard reboot by holding the power button down until the computer turns off. I am using a mid 2010 MacBook Pro with Snow Leopard. (I can't get the exact version of SL because clicking 'About this Mac' does nothing at the moment...) Any assistance or advice would be greatly appreciated.