[Hampshire] Ctrl-+ not zooming in in ff3

This is odd -
Ubuntu 8.04 amd64, recently moved from firefox 2 to firefox 3.
The keyboard shortcut for View-Zoom in (Ctrl-+) does not do anything
when I am in a firefox window.
The shortcut for zoom out (Ctrl- -) works as specified.
Ctrl-+ does expand the text size when I use it in a terminal window.
Gnome Preferences->Keyboard Shortcuts does not show Ctrl-+ being
intercepted for anything else.
This behaviour did not manifest in ff2.
What d'you reckon?