Just updated firefox to 15.0.1 and now the autofill engine is disabled.
I tried uninstalling and reinstalling the add-in but it did not work, after reinstalling there is no possibility in Firefox/Options to enable this add-in. There is only the message:
Sticky Password Autofill Engine ist nicht kompatibel mit Firefox 15.01!
(Sticky Password Autofill Engine is not compatible with Firefox 15.01)
I am using the autofill engine 126.96.36.1994.
Hope to get help...