Neither current or alpha client will open

What happened was that I played a game on the alpha client, and after that, I did some other things, and the client said it was disconnected and asked if I would like to restart or close it, I picked close since I was done for a while. Later I went to open the current client, since I was not a big fan of the alpha client, but when I tried to open it, a pop up apeared saying that I already had a version of the client open, and that I would need to close it before I could open the client. So I then tried to open the alpha client, and it did not open, no pop ups or anything, it just wouldn't respond.