This seems such an obvious reply, apologies in advance if I'm wrong, but if the checkbox to the left of Internet Explorer isn't checked, it appears to be greyed out as well.
I've just unchecked it in my CCleaner, and it appears the same as yours. In fact all the boxes appear greyed out until you check them.
Sometimes, myself included, we miss the simplest of things, and I'm pretty sure, if I'm wrong, you'll let me know. But I had to ask the obvious first.

Welcome to the forum by the way.