display posts and custom post category-wise

i used to write my blog simply by adding regular posts with certain categories and used vibrantcms theme. after the advent of ‘ custom post type’ i created one for my blog naming ‘product’ with lots of taxonomies under it. i’ve also introduced the categories taxonomy in ‘product’ custom posts.
here comes the pain……
in my theme when i click on the categories depicted in the menu-bar the posts related to that categories appear but not the custom posts i.e product. even though custom posts carry ‘categories’ , still i cant display them at under their destined category ..!!!

plz help !!