As a test/check do the following

1 Create a new page and add a Store menu module. Add required categories via module menu option 'add new category'
2. Select the Store menu module 'setting' option and goto the 'category menu settings' area and ensure the 'catalogue page' drop down list has the page you just created in point 2 above selected. If not select it and update.
3 To the same page (one created in point 1 above) add a Store Catalogue module and add a product via the modules menu option ' add new product'. Ensure the category drop down box contains a list of the category(s) created in point 1 above and that one is selected 
4 Create a new page and add store Cart module
5.Create a new page and add Store Admin module.
6.On the store admin 'store info' properties set the following
    a. Store Page: to the page you created in in point 1 above (i.e. store catalogue page)
    b. Shopping cart page: to the page you created in point 4 above (i.e. store cart page) 

If my memory has served me right then that should be you working. When you click on the a product for more detail then the same page (i.e. the one created in point 1 above) is used. i.e. you do not need to create a special page for the product detail.

Good luck
Bryn
http://www.planetspringwell.com