My macbook won't let me copy and paste things like weblinks or even sentences on MS word. Any idea why?

My Macbook pro just won't let me copy and paste or cut and paste anything. I have tried weblinks, MS word/powerpoint. It doesn't let me do it on any program at all.

I have tried the cmd + c, cmd + v keys as well as copying and pasting from the edit option in bar at the top of the screen.

Can some one help me please.

Thanks.