OMFG?!! Are you using the newest version? This is definitely not your fault. It is mine.
Please, send me the scml file (it can contain only the bone structure, if you want to keep your sprites private). Since I implemented curves, things in the SpriterPlayerInterpolator class went wrong and I only tested it with the monster scml file.
-Trixt0r
I'm using the latest version and I have send you the link to the file via ICQ.