Suddenly can't drag files

All of a sudden I can't move any files in any folder. I don't think I made any changes purposefully, but I'm still new at this. Just to clarify a little, I can copy and paste them, but I can't drag them.

This may not be a problem. If you are trying to drag a file within a single folder and finding that it doesn't move, this is not a problem. It is the way things are supposed to work. Finder is keeping the files auto arranged for you.

To move them around within a window, essentially arranging them yourself, select View, View Options from Finder's menu, and clear the check box near the bottom that says Keep Arranged By. Things will "unarrange" at that point and you can move them as you wish.

Even when I unchecked that box they don't move. For instance, I can't drag anything to the trash, it lets me select it, but not move it.

Rebooting fixed the problem. I thought Macs didn't have these types of problems?