I've this problem, too. And now the spanish translation is wrong, too.
Hello I am a Debian testing user and I use Fireefox which is named Iceweasel in Debian.
The version shipped in testing is 10.0.5 as of today.
When I try to open Kune it says that my browser is not supported.
Maybe is just because the name is different (Iceweasel instead of Firefox)? Version 10 is not so old...
Thanks
Steps to reproduce:
Open http://kune.cc with Iceweasel 10.