Transparency lost

Hi,

I’m using this plugin for frontend user avatar uploads.
My problem is that every image I upload looses its transparency.

Original:
http://abload.de/img/id_logo_neub8s7k.png
After Upload:
http://abload.de/img/1378801395-bpfullecsjc.jpg

Funny thing is that before I crop it (in the preview), the transparency is still there.
If I upload the image via WordPress and then try to crop it with WP Tools it works.

http://wordpress.org/plugins/user-avatar/