Once in a while as I'm playing, I look up at my research bar and I notice it says "no research". Now I'm not exactly sure how this happens, it might be loading a saved game, loading an auto-save, or maybe I hit cancel when I have selected a tech far down the tree which has pre-reqs. The thing that bugs me is that there is no warning saying I am not researching anything. Is there any reason not to be researching anything? If I click end turn, can I get the research window that I get at the start of the game, i.e. "your scholars must choose a path". Otherwise I spend quite a few turns getting behind the AI when I thought I was researching.
Also, a small bug: when you move the research tree around, the text stays put but the images move around.