I had that silly Ncaptcha thing affect my account a few months ago, but it's stopped now. What I used to find worked best in order to get rid of it was to click on all of the correct squares as quickly as possible, then click the blue button immediately. If I did it that way it used to work first time, whereas if I took my time to look for the correct squares it didn't necessarily work and would throw up another image to click the boxes on, even when I'd selected all of the correct boxes the first time.
If you haven't tried doing it yet delete your browsing history in its entirety, then log back in again. As soon as I did that the Ncaptcha thing disappeared and I was able to go back to logging in using only my User ID and password.