Cannot add new Asset

[Rakesh Midha]

Hello

In site->Assets section I am trying to add a jpg file as an asset, but on clicking New Asset i get an error message "The resource could not be added (see log files for details).".

In log4j.log I see I am getting an exception :
org.apache.lenya.cms.metadata.MetaDataException: The meta data element set [http://apache.org/lenya/metadata/media/1.0] does not support the key [format]!
    at org.apache.lenya.cms.repository.SourceNodeMetaData.checkKey(SourceNodeMetaData.java:92)
    at org.apache.lenya.cms.repository.SourceNodeMetaData.setValue(SourceNodeMetaData.java:99)
    at org.apache.lenya.cms.publication.DefaultResourcesManager.addResource (DefaultResourcesManager.java:152)

Any idea why is it happening and what do I need to do to get rid of this.

thanks
Rakesh