Problem with URL in Home page - names of stores are inserted into the url of pages

[Bollicina]

My site (marketplace) is based on Prestashop 1.5.4.1.

For about three months something strange happens with the url, Particularly in the categories of objects. The problem of url "magic" Seems to afflict Especially the sub-menu to the left. Here's what happens: moving from one category to another on the site (left column home), suddenly you see the error page ("Page not found - Sorry, but the web address You entered is no longer available") and all categories include empty without products / content.

This is caused by an alteration of the URL linked to the categories which are changed because names of a store/shop is inserted into the url of pages, suddenly. It seems then added to the url subcategories of the name of a store that Changes with each page load, thus giving error page.

ex.

www.domainname.it/categoryname (correct URL)

becomes

www.domainname.it/storename/categoryname  (Crazy URL)

 

If you do a test you will see with your own eyes what happens in a few seconds.

The problem seems to be related precisely to that part of the menu of categorie of the left menu (though this problem in home page occurs also in the "search" and "menu" section).

But this only happens on the HOME PAGE because It seems that on the singular pages of the product, or in other pages different by home page,  menu functions categories work (if moving us between categories items, url are not alterate).

 

Any ideas to fix this bug?

I hope thet somebony can halp me becouse is very urgent.

Edited March 6, 2015 by Bollicina (see edit history)