Strange Category Problem

Hello,
I ran into a strange category problem. I have grouped my 35 audiobooks into three categories, here they are:
– Audio Books (audio-en)
– Audiobücher (audio-de)
– Lives Audio (audio-fr)

Each category for one language. Now, after uploading to the server, two of the categories were changed automatically and I tried desperate to change them back to what I had setup, but impossible, WordPress would just not allow it. Here is what I got

– Audio Books (audio-books)
– Audiobücher (audio-de)
– Livres Audio (lives-audio)

You can see it here:
http://www.ipublica.com/category/audio-books/

I want to preserve the consistency in naming, but WordPress didn’t allow to do it. I erased all my files on the server, and reuploaded to reproduce the error and it did it three times exactly like that.

Then I erased all categories and resetup my own categories on the server installation. So far that worked. Then I had to get the posts again in the categories and here is the problem. Using the function to put several files at the same time into a category, by default WordPress assigns to each file two categories, the one I chose and ‘uncategorized’. To get the uncategorized category away I would have to treat every single post again and resave it. That really put me off and I left the categories as WordPress assigned them but this is not what it should do.

Do you have any idea why WordPress did that?
Thanks in advance.
Pierre