None of my icons drag?

I have a mid 2011 Macbook Pro with OSX Lion installed ever since I first bought it. I use to be able to click and drag my icons around easily, but I'm not sure what caused it not to happen anymore recently. Whenever I click and hold on to an icon it just stays there when I'm trying to hold on to it. It's not like the previous problems stated where the mouse would stay stuck on drag and not move to anything. This problem started happening a few weeks ago and I've never been able to fix it. Whenever I click on an icon it won't budge at all. Can anybody help?