[Building Sakai] Assignment error message

[Omer Piperdi]

One of our student cannot submit an Assignment and getting following 
error message..

2011-12-09 10:30:55,505  WARN http-8443-Processor10 
org.sakaiproject.util.ResourceLoader - bundle 
'org.sakaiproject.localization.bundle.content_type.fo
rmattedtext'  missing key: ''  from: 
org.sakaiproject.util.ResourceLoader.loadBundle(ResourceLoader.java:594)


Any idea what is causing this?

Thanks
Omer