[Plugin: Quick Shop] Checkout Page not showing in some Browsers

Hi there.
I just found the Quick Shop Plugin which really feels like i’ve hit the Jackpot because it does exactly what I need. Thanks for that Zackdesign! And I will definitely donate some money as soon as I really USE the plugin. So far I’m just testing.

And found some problems…
My products list and also checkout table and email form work fine on Firefox but are just not visible on Safari, Opera and any Version of IE.

This is my testpage (feel free to test… nothing will be bought ;-))
https://web378.server-drome.org/sandbox/schwein/

Anyone have an idea? I can’t use this if it only shows in Firefox ;-(

Thanks
Anja