Error on displaying Kanban Board (JIRA Agile)

We're using JIRA 6.3.4 with Service Desk and Agile. When we want to display one of our Kanban boards the following error occurs:

— snip —

Details
1.

• Exception: Error: History.js Core has already been loaded...
• Resource: http://btndevsrv2:8080/jira/s/a0483c1b1c4eaf2058633d280e61ed09-T/en_USd50iea/6332/120/d6d3e97754d610146a1d98bebda5b94a/_/download/contextbatch/js/greenhopper-rapid-non-gadget,atl.general,gh-rapid,jira.global,jira.general/batch.js?locale=en-US&isAdmin=true
• Line: 10085
  2.
• Exception: TypeError: Backbone['Class: JIRA.DevStatus.DevStatusModule'] is undefined
• Resource: http://btndevsrv2:8080/jira/s/a0483c1b1c4eaf2058633d280e61ed09-T/en_USd50iea/6332/120/d6d3e97754d610146a1d98bebda5b94a/_/download/contextbatch/js/greenhopper-rapid-non-gadget,atl.general,gh-rapid,jira.global,jira.general/batch.js?locale=en-US&isAdmin=true line 2776 > eval
• Line: 1
  Environment
  Mozilla/5.0 (Windows NT 6.2; WOW64; rv:32.0) Gecko/20100101 Firefox/32.0

— snap —

The error is display for about one or two seconds, then the Kanban board is displayed in the correct way. Our installation is running since Nov 2013, this error occurs since one of the updates a few weeks ago.