This same thing is happening to me when animating just images (no bones). I have a bunch of bitmaps - one of them a ninja star, The ninja star should fly from left to right while some other images are being animated. Even tho I only have 2 keyframes for the ninja star, it stops (slows down) every time it encounters another bitmaps keyframe (there are no keyframes for the ninja star where this occurs).
I'm pretty sure that this is the same issue, but I can post this in it's own topic if needed.
Any help would be awesome!
Thank you in advance