I just added to the existing thread in Bug Reports here. Basically if the enemy doesn't have TWO techs you can steal (i.e. known by them, not known by you, available to you given pre-reqs) then you get stuck in the Science Advisor screen, asking you which tech to try to steal next. I've never tried stealing tech before, and I won't again - it looks like a success gives you TWO techs, but if there aren't two, you're screwed.