This is because activities must now install to /usr/share/sugar/activities, not /usr/share/activities.
We recently synced the debian packaging into Ubuntu, and as we are going to release very soon I patched sugar in Ubuntu to look in the old location too: https://bugs.launchpad.net/debian/+source/sugar/+bug/283194 -- To UNSUBSCRIBE, email to [EMAIL PROTECTED] with a subject of "unsubscribe". Trouble? Contact [EMAIL PROTECTED]