just yesterday I put this code in my page to use a4j log window:
<a4j:log popup="true" level="ALL" style="width: 800px; height: 300px;" hotkey="z"></a4j:log>
In this case you call the log window pressing CTRL+SHIFT+Z (standard keys combination is CTRL+SHIFT+L, but in my case it opens Firebug plugin) and it's opened in a pop up window. I used it with FF 126.96.36.199 and works perfectly
hope this help
same in FF 188.8.131.52
however - I just found out that this only happens after I have opened a page that includes a google map.
After I opened up this page once, the log window will not work any longer (no matter what page)
but the problme is, that I really need the log window on the page where the google map is - any ideas?