Q Rings

might be obvious but check the little notch on the inside of the chainring is installed so it's hidden by the crank.

got a biopace triple and when i got it i didn't notice the little ring was rotated round so the extra 'push' was at the wrong part of the pedal stroke and it felt really odd, like you described.

Nice one, I didn't know about the tab thingy, will check shortly.