here's another problem I just came across.
When using the file manager I can not create new folders or access the upload folder since the page turns white afterwards.
The address bar turns into http://www.mysite.com/admin/assets/show/1?locale=de_DE
May this result from creating a multilingual site with the Translatable Addon (which I did)?
If I remove the ?locale=de_DE from the adress bar I do see the content of the Upload Folder, can create an Audio Folder
If I then try to to upload .mp3 files I do get the error: JSON unexpected character.
This fix here didn't work out since all my folders have the right permissions: http://www.robertclarkson.net/2012/11/silverstripe-3-file-upload-error-json-bad-character/
If someone can help out here, I'd be very happy.