Skins don't work

Hi,

your plugin looks really great, but I have a little problem with it.
Despite the fact that I haven’t change anything in the files and I have all four folders in len-slider/skins, in a WordPress I can’t change skin for a slider. I have only default and it doesn’t work.

I converted one of the folder with the skin into .zip format and tried to upload it with the len-slider admin panel (upload a skin) but it didn’t work. All I got was “Uploadable zip-file is invalid: invalid archive mime-type or incorrect name of skin zip-archive.”

Could you help me?

http://ww.wp.xz.cn/extend/plugins/len-slider/