Lars,
please disable firebug and see if it still happens,
Everyone,
see if you can reproduce this bug by running firefox in safe mode by opeing a terminal and typing firefox -safe-mode.
Russ,
Your issue looks like its gmarks that was causing it. this may not be the same for everyone but either way we are unable to support extensions we dont package.
Lars,
please disable firebug and see if it still happens,
Everyone,
see if you can reproduce this bug by running firefox in safe mode by opeing a terminal and typing firefox -safe-mode.
Russ,
Your issue looks like its gmarks that was causing it. this may not be the same for everyone but either way we are unable to support extensions we dont package.