[Dart_Xerpoth]

that happens to me sometimes, though in other place in the game. I haven't got up to the Trayus Academy yet but my advice is:

1 Try pressing Ctrl Alt Del it will bring up the task manager, then just go back into the game (dont quit the game though)

2 If that doesn't work save before you try going through the door and if it freezes up just quit and try again, if you persiveer it might let you go through