I was copying some text by Ctrl-dragging and an information box popped up giving me information on the word I was dragging. Normally this isn't a problem but this time I was trying to drag to a position on the next line directly under the info box. Every time I got to that position, the cursor changed to the circle-with-a-slash and wouldn't let me do the copy. I gave up and did a copy-then-paste instead.
For the next release, you may want to fix this so that SE closes all info boxes when a drag is being done with a block of text. I don't think anybody needs an info box up during the drag.