Hi,
By chance are you using IE8? Can you produce the problem in other browsers?
There was previously reported some issues in Shared Files using IE 8 here. Where events would fire more than once. This particular issue has been fixed in NeatUpload and will be fixed in the next release of mojoportal. In the mean time it can be worked around using IE8 compatibility mode.
If you are not using IE8 or can produce this issue in other browsers please let me know and I will investigate.
Best,
Joe