[Digikam-users] Read/Write to sidecar files is grayed out (Digikam 2.6.0 on Gentoo)

[Carlos]

I have installed Digikam 2.6.0 on a Gentoo system using Portage.
Everything seems ok, except that the options 'Read from sidecar files' 
and 'Write to sidecar files' appear grayed out so I can't enable them.
Also, when I activate metadata info for an image (using the metadata button on
the right side bar), I can see tabs for Exif, Makernotes and IPTC info, but the
tab for XMP info does not appear.
Any clue what could be the cause?