MacBook Late 2008 (Unibody Aluminum) running Lion cannot shutdown, restart, or logout

After upgrading to mac os x lion, my macbook has not been able to restart or shutdown or even logout properly. This problem was not present when the laptop was in snow leopard. Currently, I am able to do a shutdown through the terminal by using the command:

sudo shutdown -h now

or restart by using the command:

sudo shutdown -r -h now

This is fine for most situations but when I am trying to install an update or a program that needs a restart, I am unable to do so. When still at the login screen, I am able to shutdown properly leading me to think that a process is preventing shutdown but I can't find anything in the console. The power button also becomes unresponsive (normally pressing it brings up the window asking whether to shutdown, restart, etc.) and can only be used to do a forced shutdown (i.e. holding it down for 10 seconds). The sleep, restart, and shutdown functions in the apple menu also do not work.

Any ideas anyone?