Command + Q not working

I got my macbook pro last June and I love it. But lately it's been acting kinda funny. Sometimes when I try to quit my browser (firefox) the command + q won't work. Sometimes the drop down menu works and other times it doesn't.
Also, sometimes when I start up (after shutdown) my finder will pop up for no good reason.

Any input would be appreciated. Thanks in advance.

I've had similar problems with an occasional application. One thing that might be useful is to repair disk permissions using Disk Utility. You could also try reinstalling Firefox. On a related note, do you happen to use Spaces? If so, this could mean that a pop-up window is appearing for Firefox in another space, which would interfere with the quit command.

Also, what do you mean by "my finder will pop up for no good reason?" Does that mean that a Finder window opens? If so, that is actually normal behavior as far as I can tell. I believe it is simply the normal response when focus is given to Finder.

-Nik