User friendly URL 404 - Page not found on two languages (probably after server change)

[rugydp]

We have a shop running with four countries and each of the four countries has four languages activated, DE, FR, IT and EN. User friendly URLs are activated. We are running the site on an production server and on a testing server hosted at the same provider on different servers. It seems that on day X they switched to a LiteSpeed Web Server for performance improvement. 

 

Now the strange Problem: since day X we get a 404 message only on categories for two languages (DE & IT) in any country on both environments. All other user friendly URLs work in any country in any language. 

 

The hosting provider can't switch back and can't help either.

 

We tried to regenerate .htaccess many times, reload the language, changing names of the categories and and and... nothing changes. We run the shop in "not user friendly" mode for the moment.

 

Any ideas someone?

 

Thanx a lot.

Edited February 11, 2015 by rugydp (see edit history)