Error when unpublishing nodes

Hi,

I have a set of nodes which I want to un-publish. Some of them include the track-field. When I select them (bulk select in content listing) and unpublish I get the following error

An error occurred. /en/batch?id=31&op=do
Fatal error: Cannot use object of type stdClass as array in /home/purevelo/www/d6/sites/all/modules/trackfield/trackfield_file.module on line 31

thanks
Rich