Indeed. The issue was that I had made an appointment for a specific time and location. However, the office was listed as being closed at the time of the appointment - hence my issue. I certainly didn't want to be a no-show and lose my $100 fee (as you would if you cancelled the appointment). I did try rescheduling - but no appointments available (in person or online), and did try to call their helpline and local number. The local CBP office stated their office hours on the web (i.e. it would be closed), the helpline was of limited use. After 1 hour 10 mins on hold to the helpline - without getting past the mind-bogglingly badly looped music, and juggling a couple of phones, I got through the to local CBP office. They said, "oh yes, the office hours on the telephone message is wrong - we open at 9am...". Another DOH! Anyway, sped up to their office and got it all sorted.
Moral of the tale - don't believe the web/telephone messages!