ubercart 6.x-2.0-rc6 and internationalization don't work together smoothly

I set-up a new page with internationalization and ubercart together.
As long as only "Conditional Actions" and "Store" are activated, Internationalization works. If you activate Cart, Order and Product Internationalization stops working in some ways: if a user logs-in in another language than English, the address changes to i.e. http://www.example.com/de/de/user/1 which shows "Page not found".

Is there any work-around for this or can you point me in a direction how to solve this issue? I do really need Ubercart to be working with different languages.

Thanks a lot for any help!
Ashok