Firefox ignoring it's own preference/settings in 12.10

I am trying to turn off two things in Firefox - it is re-opening every tab that was open when it was shutdown, and it always warns when I close multiple tabs.

I have altered both these behaviours in preferences (I set it to open just one defined home page on startup, and I unticked the multiple tab warning box), but Firefox is ignoring the changes.

I tried the reset Firefox button in the troubleshooting page, but it still misbehaves.