Also ...  Started to happen yesterday, 10/19/08.  First just  got the page withe the 'zero'  when using  Google, now have this  same  'kitchensinks.nOt'  certificate appearing internittently whenever I attempt to enter or exit  gmail. Re-installed firefox which removed the problem for about six hours and now its back in the new instalation!

Wonder if it  is some kind of 'keystroke copier'-- my browser has been restricted to only using the keyboard for copying, not cut and paste!