Same problem as realidan2, danatang and thesandeepgoyal.
From what I can understand, if imagerotator.swf is appearing, but always stuck in the "loading" screen, then that means it cannot find either the XML or the images. So the position in the folder structure as it relates to those files is important.......... BUT i long to see someone explain it clearly :(
For me, I have decided to put all my galleries inside a folder named "whatever", instead of having them accumulate in my website's root (that's an option I can change in the NextGEN options). I did try both ways, but still got the loading screen.
I tried diffrent locations for imagerotator.swf, didn't work either, got the loading screen, nothing more...
How about the creators of NextGEN and/or imagerotator.swf help us clarify this, instead of all of us scratching our heads in vains... :(