1.4.0.3 Products Category Module and Cross Selling Module no showing up

[Mav]

I tried everywhere to install two built-in Products Category Module and Cross Selling Module, but they both failed to load up on the product page although I've put in tens of orders.

But the funniest thing is: I have a shadow site copying all the same code of version 1.4.0.2 connected to the same database but put in a different domain, every time when I setup on my main site for these two modules and that shadow site showing these two modules or inhibiting these two modules.

Can anyone help me out on this issue since these two modules are extremely importantly in taking full advantage of current visitors/customers?

Thanks in advance.

[Mav]

BTW, I've deleted almost all other modules but left a few necessary built-in ones without any third-party modules, but still still no luck at all.