Ran into this issue (it's even worse with Firebug 1.9) and put a hacky
fix in since we need it to work properly with GTmetrix. Here's the
patch we're using:

--- yslow-3.0.4/chrome/content/yslow-firefox.js 2011-08-08
13:15:15.000000000 -0700
+++ yslow-3.0.4-gtmetrix/chrome/content/yslow-firefox.js 2012-01-05
17:14:13.000000000 -0800
@@ -112,6 +112,16 @@
}

if (typeof Firebug !== 'undefined') {
+ // There seems to be some sort of timing issue with YSlow and
+ // Firebug which causes an error in YSLOW.FBYSlow.init(),
+ // "YSLOW.firefox.startup():TypeError: FBL.extend is not a
+ // function". Hack around this by retrying the call to
+ // YSLOW.FBYSlow.init() if it fails.
+ if (typeof FBL.extend !== 'function') {
+ YSLOW.util.setTimer(function() {
YSLOW.firefox.startup(wmode); }, 10);
+ return;
+ }
+
try {
if (Firebug === null) {
FBL.ns(function () {


I'm not sure why FBL.extend isn't set up correctly sometimes and I don't
know enough about Firebug internals to fix it properly. Hope this helps!

Adrian

On 01/06/12 02:57, Darren Person wrote:
> Hi Betty,
>
> Has there been any update on this bug? The Firebug team has offered to
> assist in fixing it. http://code.google.com/p/fbug/issues/detail?id=4970
> - Please see comment #9.
>
> Thanks!
> -Darren
>
> --- In exceptional-performance@yahoogroups.com
> <mailto:exceptional-performance%40yahoogroups.com>, betty tso
> <bettyytso@...> wrote:
> >
> > hi Darren,
> >
> > Thank you for providing detailed steps to reproduce the issue.
> >
> > We've found that user has to completely re-install FF8, latest
> Firebug and YSlow to make YSlow work once user updated to FF8 and latest
> Firebug.
> >
> > Thanks for filing the bug with Firebug; we'll also try to find a
> workaround from YSlow side to take care of this. Will keep you posted.
> >
> > thanks,
> > -betty
> >
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > Engineering Manager, Exceptional Performance
> > 701 First Avenue, Sunnyvale, CA, 94089
> > ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> > "I don't believe in the no-win scenario." - James T. Kirk from Star Trek.
> >
> >
> >
> >
> >
> > ________________________________
> > From: Darren Person <dsperson1@...>
> > To: exceptional-performance@yahoogroups.com
> <mailto:exceptional-performance%40yahoogroups.com>
> > Sent: Monday, November 21, 2011 12:09 PM
> > Subject: [exceptional-performance] YSlow plugin does not always load
> after reboot - Firebug or YSlow?
> >
> >
> > Â
> > Reported to Firebug as well:
> http://code.google.com/p/fbug/issues/detail?id=4970
> >
> > TEST CASE:
> > - YSlow installed an configured to autorun with each page view after
> page loads. Typically works when Yslow is installed within the same
> session or instance of firefox, however, when firefox is rebooted, yslow
> plugin doesn't appear to get loaded into Firebug.
> >
> > Detailed STEPS TO REPRODUCE the issue
> > - Installed Firebug & YSlow add-on into Firefox
> > - Chose Yslow "Autorun" feature - right click in status menu, "Autorun"
> > - Start Firefox and visit any webpage (notice Yslow tab in Firebug)
> > - Shutdown the browser and restart Firefox (maybe two or three times)
> > - Yslow no longer appears on the Firebug Add-on Menu nor runs.
> >
> > Expected result - Firebug should open with Yslow plugin and run upon
> load of default "homepage". Instead, Firebug loads and YSlow appears to
> be disables / doesn't run.
> >
> > I've tried this with multiple versions:
> > Browser: Firefox 8
> > Addon-on: Firebug 1.8.4
> > Addon-on: Yslow 3.0.4
> > OS: Windows 7
> > OS: Windows Server 2008
> > OS: CentOS.
> >
> > Note, this is happening after several reboots post installing YSlow /
> Firebug (re-start firefox several times in a row). But once it happens,
> it doesn't come back unless you re-install Yslow.
> >
> > When the failure happens, YSlow isn't listed in the Firebug toolbar
> anymore. Also, the YSlow icon in the right bottom corner of the browser
> shows the YSlow icon without the "YSlow" text to he right.
> >
> > I've tried this on Windows 7, Windows Server 2008 & CentOS without
> issue. I've even tried it on a VM at Amazon to make sure it wasn't
> something environmental. let me know if you are able to re-produce.
> >
> >
> >
> >
> > [Non-text portions of this message have been removed]
> >
>
>