When pressing I, I now receive:
keying set failed to insert any keyframes.
No idea why pressing I doesn't work anymore. What did I do wrong? (I've upgraded from 2.71 to 2.72 and it stops working).
See screenshot: The solution was to remove the keying set at the bottom and when selecting the camera, to remove the 2 keying sets that were there.
I however have no idea how this was enabled, and at this point of time I also don't know the goal of this keying.
After removal, the I key worked again.