Hi, I've found a strange bug in the 2.65 test build.

1. Open the attached file: cancel_render.blend.
2. Select Render -> Render Animation.
3. Start left clicking on the F-Curve Editor like you would want to go to another frame.
4. BUG! Rendering stops after one to couple of clicks.

I'm not sure why it stops sometimes after first left click, sometimes after few tries. I've found this when I've accidentaly clicked that window while rendering long animation. Suddenly, almost at the end of it :-/

Another weird thing is that Blender's icon still has this progress bar indicating rendering. Render stops after the click and the bar is still there.

P.s. I've tried this on Mac OS X Mountain Lion.