What version of Firefox??
And are you using the Megaupload Toolbar? a quick google search led me to the point that it is due to the megaupload toolbar.
Removal Instructions :
In Mozilla Firefox: Navigate on the browser menu bar to "Tools" then "Addons" then "Extensions"
Select "Megaupload Toolbar" with the mouse
Select "Uninstall" and then "OK"
Close all Firefox browser windows
The Megaupload Toolbar will be gone when the browser is re-opened
and hopefully, the "TRYING TO LOAD A NON-LOCAL URI" message won't appear anymore
Abhas added 4 Minutes and 16 Seconds later...
or, you can simply disable the toolbar using the same method, enable it when you require.