first thing to try (if you haven’t done so already): re-save the pages WPPizza has created
(I’m NOT talking about the WPPizza Categories and Menu Item Pages, but the pages that display a list of your item – typically a page that has somthing like [wppizza -some attributes-] on it)

make sure your theme (or one of your plugins) does not use an old version of jQuery (some themes/plugins override the version that comes bundled with wordpress – no, i don’t know either why they would do that)

If that still doesn’t help, you might have to adjust the CSS (see ‘Can I edit the css ?’)

If you have problems, send me a link to your site I’ll have a look…