I encountered two conditions making the module unable to upload any further images:

1. when Imagemagick fails to process an newly uploaded image.

2. when uploaded file is not in allowed format.
I firstly uploaded a bmp file, then it prompts the format is not allowed. Since then EVERY upload encounters the following
message:
impossible to move powerpuff_jp.jpg uble to move powerpuff_jp~0.jpg to albums/userpics/10002/!

thx
--bee