how to debug tabs with custom theme

Hello,

I have a mulit-site environment where fieldgroup tabs will not work on one site with firefox 3 but will work in opera and ie 6/7. My other sites do not have an issue with tabs so it is not modules installation.

I have a custom theme that I am using for the site having the problems so it is obviously something with the theme. When the user clicks on the tab, the url changes to http://10000littleideas.iproposecleveland.com/node/add/lightingfundingid... .

Can I please have some suggestions on how to debug my issue?

thanks,
G