Select an area of a canvas, invert the selection, then click Image > Crop. Nothing happens. Crop tool only crops original selection (interestingly, cropping still works if one inverts the selection again, back to the original selection).
I should have been more specific: This occurs even when the original selection extends to 3 of the 4 sides of the canvas.
Imagine vertically selecting 3/4 of the whole canvas (so only the lowest 1/4 is unselected). Then invert this selection, so the lowest 1/4 is now selected. Applying Image > Crop should crop the canvas to the lowest 1/4, since the original selection and the inversion never intersected (if it sounds confusing to read, it'll make sense if one tries it out).
I've tried it in Photoshop CS5 on the same machine, and it works as described.