Same problem here (crashes/hanging upon event completion/waypoint add, plus inability to activate glider mastery).
The interesting part is, I first achieved the required number of points on one of my characters (Piken Square: Anatasja), then immediately went to the mastery screen, and saw that I could click it (the mastery button was lit up in gold). I realise that the skill is unlocked for all characters in the entire account, but out of homage to my main toon, I decided to press the button while playing as her (Piken Square: Artawen). When I went to the same screen when logged in as her, I experienced the bug, and couldn’t press the button (which now wasn’t coloured in gold). Message is: need 0 more mastery points….
Hopefully this information can help you identify the cause of the bug.
p.s. kicking myself now – should have clicked the mastery button while I had the chance
(edited by Breton.2834)