On https://www.wikidata.org/wiki/Q15498450?debug=1 I get the following JavaScript error:
TypeError: wb.datamodel.Fingerprint is not a constructor
That script was not loaded, according to the network debug tab in Firefox.
Happens for me on Firefox 34.0, does not happen on Chromium. Someone else couldn't reproduce on their Firefox.
Also happens on a fresh Wikibase/Mediawiki installation.