Can't add any media in Document and Media page under Control panel

• Type: Bug
• Status: Closed
• Resolution: Fixed
• Affects Version/s: 6.1.0 CE GA1
• Fix Version/s: --Sprint 11/12, 6.2.0 CE M2
• Component/s: DM, Frontend Infrastructure, Legacy, Legacy > Control Panel menu
• Labels:
  • community-verifier
  • documentLibrary
  • javascript
• Environment: Windows XP, tomcat7, java 1.6, firefox 9.0.1

When I go to Document and Media page in the control panel, firefox throws a javascript error : "l is null".
When I click on buttons (add, sort by or manage) firefox throws another javascript error : "Liferay.Panel is undefined".
Drop down menu doesn't appears, so I can't add (sort by or manage) any document or media.

I tried with IE 7 and I works perfectly...

I seems this is firefox issue.