Can't access existing files with IMCE

Hello,

I have a content type 'Photo' with an image field. I uploaded several photos using this content type. All files are in the /sites/default/files/pictures folder. However, when I access the file browser, it does not show any files. What am I doing wrong? The permissions for that folder are set to 777 and the folder in the IMCE profile is set to root/sites/default/files/pictures.

The same happens with my private files folder at root/sites/private_files. No files show up in the IMCE browser.

Any help is appreciated.
Thanks a bunch!