Hi ,
there is a problem with manufacturer sorting when you have Joomla SEF URLs enabled. The first time you choose an manufacturer to sort the results at the category browse page it works fine , but if you try to sort again by choosing another manufacturer then you get no result . If you disable the SEF urls everything is ok.
Take a look at this example:
First time sorting by manufacturer URL = hxxp://localhost/2.5-vm2/manufacturer/kataskevastis-1/katigoria-1.html
Second attempt to sort by another manufacturer URL = hxxp://localhost/2.5-vm2/manufacturer/kataskevastis-2/search/katigoria-1.html
and you get empty results.
It seems that the word "search" that gets between the category and the manufacturer is the problem, if you delete it from the url then you get your results.
Works perfectly for me in two languages. From my experience this kind of problem is caused by faulty entries in the Joomla 2.5.x database table. A few days ago I had something similar when a wrong VM2 category name always showed up in the url while filtering manufacturers. In my case it was a faulty menu entry in the Joomla 2.5.4 menu table. Deleting that one from the menu administration didn't work. I manually had to delete the corresponding entry in the database, and then re-added a new menu item in the backend, before it started to work correctly again.
I updated my test installation to version virtuemart 2.0.3.J and it works fine now.