People are looking into this. For the sake of due diligence, in the meantime I'm going to point you to this thread:
Note that the game may not launch or work properly after we release a new build if you use a third-party program, due to possible incompatibilities. Customer Support cannot offer support if a third-party modification breaks, interferes with, or prevents you from playing Guild Wars or Guild Wars 2.
This may be what some of you are running into.