I had a similar problem when running TurboTax inside a virtual machine. If that happens to be your case try to switch the VM into full screen mode, this should make the entire dialog visible, including the buttons at the bottom.
Otherwise you can try to use the TAB key, trying to find the right button blindly and confirm with RETURN. When I tried that I ended in a similar loop though.
I had that problem with two screens. (and I also had the problem last year! TurboTax please fix the windows! I reported it to them!)
I moved the taskbar from the top of the screen, which showed more info; but that did not help!
After much monkeying around I found a Rube Goldberg solution!
After filling out the page, I hit the tab button several times, bringing it to the top continuing down the page; once the tab was on the last thing on the screen I then HIT THE TAB 4 MORE TIMES; THEN HIT ENTER!!!! (or after entering the last item hit the tab 4 times, then enter)
If you only tab it once or twice it opens up a turbo tax web page in your browser, if you hit it 3 times it hits the back button and you get to start over!!! but hit tab four times it finally gets to the continue button which is hiding off the screen.
On the third screen where the back & continue buttons are on the screen, you can tab and see what the tabbing did on the previous pages.