I have the same problem here (Mac OS X 10.9.2, Spriter b6.1).
Since you are using Qt, you are probably experiencing this issue (QImages are generally not initialised after creation):
http://stackoverflow.com/questions/1346 ... -has-noise
So, this might be all you have to do after creating a QImage and before drawing the individual bitmaps onto it:
image.fill(Qt::transparent);
I also tried to export my project under Windows XP which resulted in a crash..
Finally, I tried it under Linux which worked flawlessly. This might just be a lucky 'coincidence' due to differences in memory handling though.
Anyway, thanks for a great tool. I can't be bothered with single-platform tools anymore these days, so I was very happy to find your project.