Pedro-
Not a complain, just a bug notification.
This is a bug in Mozilla. It appears in all such toolbars I've seen (in fact ours at least gets the cursor position right). I have reported it and all we can do is wait for the Mozilla development team to fix it. IMHO it is not so severe to justify disabling the toolbar, as 1) it happens only in Moz, 2) you are still in the right position after you move the cursor.
Regards,
Erik