[Nepomuk] nie:depiction problem

[Andrew Lake]

Whenever I try to set the nie:depiction property on a resource object
- created via Nepomuk::Resource artworkRes(artworkUrlString) - I'm
getting the following Nepomuk message:

Nepomuk::ResourceData::setProperty: "Cannot set values for abstract
property 'http://www.semanticdesktop.org/ontologies/2007/01/19/nie#depiction'."

Additionally, even though resource object passes the
Resource::exists() check I'm getting:

Nepomuk::ResourceData::setProperty: "setProperty: No two resources can
have the same nie:url at the same time."

KDE v 4.8.2
SDO v 0.8.1

Any ideas?
Andrew