Thanks a lot!
Actually I use Avast, so it’s probably that.
Anyway I’ve found this: http://community.wd.com/t5/WD-TV-Live-Streaming/Wierd-issue-not-sure-of-cause/m-p/391269#M7848
But I can’t find a solution.
I disabled Avast for 1 hour, but I still can’t see other files. Do I have to uninstall it and try something else?