same problem here
It somehow doesn't replace the language path, but adds another one instead like:
/de/...--->/de/en/....
or if I click on the language that is already active:
/de/...--->/de/de/
which gives me, of course the same error as mentioned above: "article not found"
are you sure it is one of the plugins? what could it pssibly be, even if i choose th standard template beez5 which comes with the joomla instllation it doesnt work....
could it possibly have anything to do with an joomla update, perhaps to 2.5.9 or something like this?
greetz and best regards