Lately it's always there...
Using win 7 us x86 with reader 10.1.7. Have seen this on multiple machines.
I wish I knew. It is so annoying. I have 11.0.3 on XP. i looked through every menu without finding anything likely.
And what interface genius removed the close button from the About panel, so you have to fish around and find something to click on to get rid of it.
Ah, I found the answer on the web. Click on Tools.
I hated that pane but now I kinda the miss it
The Tools button will toggle it back for you.
Just hit the [Esc] key!