Extra unwanted bit in Firefox browser

After a restart of the computer (rare ) Firefox is kindly giving me a blank 'extra inch' at the bottom of the window below the status line.
Its got nothing in it except a red inverted v on the far left about a cm up from the bottom of the window. This area does not resize when you shrink the window.

Wh 'appen?

[TSM]

Seems the FF config has corrupted.

Start it holding the Shift button down, this runs it in safe mode to see if it all runs fine that way.

To clear firefox settings and start again but keeping all your bookmarks etc...

Start->RUN-> %USERPROFILE%\Application Data\Mozilla\Firefox\Profiles

This will open up a folder that should have one extra folder inside, open into that folder. You should see a file called prefs.js or just prefs, rename it to prefs_old.

Now restart firefox.

Thanks will give it a try when I get into work.

Whilst we're on the subject of Firefox problems, I find that the AA website is rendered completely wrongly by Firefox on my work PC (Win XP). It's fine with Firefox on my Mac at home. All other websites work OK with Firefox, just not the AA www.theaa.com

Can any XP/Firefox users let me know if it works properly for them?

All fine here in FF And XP.

@wyrness.

Seems fine here. Firefox 2.0.0.9 , XP Home.