I use fancyBox (v2.1.5) and work with Firefox version 35.0.1 and Firebug 2.0.7. When I open the Firebug window fancyBox is not working anymore. Are there any settings I could change to get it to work?
I have the problem also on the official demo page.
FireQuery 1.4.1 is known to cause JavaScript execution problems in combination with current versions of Firefox and Firebug 2.0.*. This is also mentioned in the Firebug FAQ.
As FireQuery development is abandoned, you need to disable/remove it to get your page to work correctly.
Note that part of FireQuery's functionality is integrated within the Events side panel Firebug 2.0.