Are you sure you want to Leav thie page error

Recently WP has been giving me this JavaScript pop up message almost EVERY darn time:

“Are you sure you want to navigate away from this page.

Changes you have made will be lost”

The crazy part is that even if I have JUST updated it still
gives the message. Never used to happen.
Is it a WP thing or a Firefox thing?
tried deactivate all plugins to see which one ws creating error but it still didn’t go away even with all the plugin deactivated.

So what do do now?

This is occurring in any browser FireFox. I tested IE7 Chrome same thing