I've noticed that, when teleporting (notably, between dimensions) my experience sometimes disappears and resets to 0. It is not gone, as a quick relog returns the xp to where it should be. I can verify that the xp is actually gone, as trying to enchant with 0 xp (after then glitch when I should have 30 levels) does not allow me to enchant anything until the xp is restored by relog.