When attempting to login to a webpage that LastPass doesn't recognize, it offers the Form Fill screen when you click on the ...] This is usually no help because the unrecognized webpage is not associated with a saved FormFill. The big problem is after this Form Fill screen appears, there is no way to get it off the screen. It's stuck, open. And no amount of clicking on stuff removes it. So it essentially blocks any further activity on the webpage, making it impossible to log in. And the reason that I'm clicking on the ...] icon is to see whether LastPass can fill-in the missing login information for the page. So, I'm stuck. Here's a screen-shot.
Could you try to uninstall the LastPass Extension, then reinstall from here to see if that resolves the issue? https://lastpass.com/download
If that doesn't work, when that Form fill window is showing, are you able to click in to any of the fields LastPass is trying to fill in to, and then hit the Escape key on your keyboard to get that window to close?
Does this also happen when clicking the LastPass icon in your browser toolbar, instead of clicking the LastPass in-field icon?