Context Menu Integration impossible

Hi !
First of all, a big thanks for Subdownloader. It makes the search of subtitles easier.
I always have used the 1.2, but I discover today that a 2.0 is available.
But with the 2.0, I can"t use the context menu, which is for me the easiest way to use SubDownloader (right click on the movie, and it's done). I see the box to enable it in the option menu, but the box is grey, I can't tick it off.
What am I doing wrong ?

Thanks.