UPDATE: After investigting this I have concluded that the problem concerns ALL new image styles, but "old" ones are still working. Old ones are the built-in (e.g. thumbnail) and one image style of my own.
Also: I use the patch to create the in core/modules/image/image.module, if it is a factor.
I have run a really strange problem: New image styles I have created don't work on one server (of course the production). I have tried to re-create the image styles, flush the caches etc ad nauseaum, but still the same thing. I have an exactly similar (apart the dimensions) image style that works just fine. The file permissions and owners are the replica of the working one...
The effect is Focal Point Scale and Crop (working dimensions 550 x 250, non working 1290 x 400). And in the development it's working just fine.
Any ideas, anyone?