It seems that the issue is related to using Nginx web server and not Apache. I guess the url rewriting part (which is NOT controlled by .htaccess, but rather by nginx-specific configuration file) is misconfigured. I've installed this plugin http://wordpress.org/extend/plugins/...compatibility/
but still no luck.
The easiest solution to fix the problem is to copy and paste the store CSS into your theme's CSS file. You can find the default CSS here: http://www.datafeedr.com/docs/item/172
Be sure not to copy the numbers. You can select and copy all of the code you need by clicking the "copy to clipboard" icon:
Just paste that code into the bottom of your theme's style.css file or create a new file and link to it in your header. That should solve all the issues you are having.