I've tried half a dozen times friday night, and same attempts tonight to pre order. Responds with a generic Error message most of the time, occasionally send me to my account page. Multiple guildy's are experiencing the same thing.
While they are having server issues; I would advise you and your guild mates to not make any purchases until things are calmer.
Same thing again tonight, tried to preorder a half dozen times, still getting a generic "Error" message. Others are reporting the same, while most were able to pre order and get into Beta. /Facepalm