Why is there suddenly an X next to my patch tool?

I have CS6 and I use the patch tool all the time. Today I went to use it, but I wasn't able to move what I had circled to a different location on the image. Then I noticed an "X" next to the patch tool that hadn't been there before. I tried playing around with the selections on the upper lefthand toolbar, but nothing I selected let me use the tool like I've been doing. I have no idea what I could have changed, and after years of using PS, this is the first time I've run into this problem. Btw, I'm not a professional user; I just use it for minor photo adjustments, so please don't get TOO technical,

Any suggestions?