Same issue here on Mozilla-build Linux 30 on Ubuntu with Firebug 2.01 (so Firebug update to 2.01 alone doesn't appear to fix the error). Only happened when the page wasn't being viewed while the JS was loading as I switched to a new tab.
If I understand correctly, the issue has been fixed in Firefox 31? (Issue 7359 - https://code.google.com/p/fbug/issues/detail?id=7359). Good catch BTW. Never would have suspected Firebug (i had the same error except in my Google JS the V is a W for the same function? The most frustrating things was that the error didn't appear unless I re-attached behaviors in my Drupal app via the console. ReferenceError: W is not defined -- You received this message because you are subscribed to the Google Groups "Firebug" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To post to this group, send email to [email protected]. Visit this group at http://groups.google.com/group/firebug. To view this discussion on the web visit https://groups.google.com/d/msgid/firebug/0c4601c0-f61b-4074-a99d-ce781f289ad2%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
