I can second that. I just got my weekly activity bonus which almost filled up my daily exp bonus.
After walking through a portal I got - xp displayed in the top right.
I cant tell if it took xp away for real but my daily xp bonus got reset completely.
Edit: Now that i think about it. I have got the weekly activity bonus early (at 4/5), just by walking through a portal (to a different world?).
Edit 2: It happend again on my main Character: Got the weekly activity bonus early by walking trough a portal from therka to munteen. Got the exp. Walked trough a other portal, Weekly xp bonus was removed again and weekly state is back to 4/5.
So i didnt gain or loose anything, but its very confusing seeing that you just lost several thousend xp.
Edit 3: This bug might also cause that the daily/weekly feats are not trackable (right click) during this play session.