Translation problem of managing the "front shop" translation after upgrate

[sf-webdesign]

Hi all!

After upgrading to Prestashop 1.5.5.0 I got a problem with the translations. I am not able anymore to manage the translations of the front end. This means that i cant edit them. (See attachment). It states that there are no expressions..
However, it is still possible to manage/edit the translations of the backend.

Anyone with a solution? or is this a bug?

Thanks!