OK I finally could access my map:
I had to create a .pk3 archive in my path, with my map in it. So basically it just wouldn't work if it was in a directory, but it works fine inside a .pk3...
By the way, it works either in ~/.openarena or in /usr/share/openarena (where the binaries are), as both are in OA's path.
You can check what you path is easily by issuing the "/path" command in the OA console.
I'm curious however, does this happends to me only, or do all linux users experience this problem? It's pretty weird really.
Thanks for your help folks, now I can get back to mapping
- trib'