Recently, whenever I try to click using trackpad or a mouse, it doesn't work for some cases. For ex. trying to open a folder or trying to play a song on itunes. So whenever I want to play a song or open a folder, I need to tap it a bunch of times. This problem only popped up when I plucked in my USB mouse into my macbook. I use a Macbook Pro 13-inch and it is a Mac OS X Lion 10.7.5. Please help me 
