HELP: cannot load pages… though it seems I can!

Hi,
I’d like to open a new thread for this issue because is quite big and annoying.
If I try to navigate through, say, my Company menu jumping from one page to another (e.g. Mission, Quality etc.), or from one post to another, it happens that it seems to load the page but it stands still on the page I’m already in. Url also changes, e.g.: I’m on http://www.mysite.com/company and I want to visit http://www.mysite.com/mission, page seems to load, url changes from the first to the second, but the page shown stays the same.
It happens on more browsers. And happens using both the main menu and the menu on sidebar. I tried to empty my cache (W3 Total cache) but didn’t fix it.