My character can not access icecrown

after picking up the quest "the last line of defense", a quest which is known to be bugged (yet listed as fixed on the bugtracker?) my character would begin to be stuck on invisible platforms/walls and have to be alt f4ed into a character unstuck (hearthstoning does not work).

obviously after seeing this bug i abandonned "the last line of defense", however if i fly to icecrown (including flightpaths and flying manually) the bug returns in the exact same form. this means i can not access **any of icecrown** without making my character unplayable

i'm not sure if this is the right forum for this but i'd really appreciate if there's a way to fix this(?) whether it's by autocompleting that quest for me or any other means

thank you.