Based on newsgroup postings, users did not get the news that Firebug 1.4 requires a manual reload the first time you open it on a site. Ok, no I don’t know how they would know. So here it is:
In 1.4, when you open Firebug on a page it does not automatically reload the page. You have to do it manually.
In 1.3, the page was reloaded for you. We made this change because some users (ok it was Steve ;-), complained that the reload was not always necessary and sometimes wastes time. This is especially true for users who are primarily interested in HTML and CSS or for users who want to know just when the reload is triggered so they can watch how the page loads.
But why do we need to reload at all? Well to track net traffic, to track script loading, and to listen for console logging we have to add listeners on the page before the page load begins. If Firebug is not active at the time of page load, none of this happens. So after you open Firebug you have to reload to get all the info. That was true in 1.3 and it still true in 1.4. The only change here is that 1.4 you have to do it manually.
By now my brain automatically hits reload when I open Firebug, since I always want all the info on all the panels