Xfce 4.10 - Default browser ignored on help

Sorry if this is already answered. I did search but couldn't find anything. I have 4.10 on Fedora 16. When I click on a help button it opens in Firefox even though in Default applications the default browser is set to Chrome. I have checked in the Mime Type Editor, great addition to Xfce by the way despite the name, and there is no mention of Firefox anywhere in there. Not sure where else to look.