Upgrade of Nice Menu breaks the layout

Hi all,

I need some help to clear up the damage that http://webdesigncompany.org/ did! (don't use them)

They developed a theme for us. It was installed in the core theme folder! After a lot of debugging, I've got it almost completly moved to sites/all/themes

There are a few issues left, but the major one is with nice_menus. The site uses 2.1 and after I upgrade the module to 2.3 the menu isn't working anymore. It appears that they editted the nice_menus.css in de module folder. So I copied that file to the theme folder and used the "Path to custom Nice menus CSS file" setting to enable it.

Now it shows (a little) bit of the styling, but not all. I don't now what else they edited in the module or so, but when I look at the dates of the files, only nice_menus.css and arrow-down.png have another timestamp.

I really would appreciate some help as I am no css specialist at all, and correcting the theme to maintainable status drives me nuts!

The production site is www.beetsbv.com and the upgraded site is staging.beetsbv.com

Thanks in advance!