A present for you BW:
http://fah-web.stanford.edu/serverstat.html
(a good thing to have bookmarked AND available at the top of this page; i.e. Server Status)
This is a Collection Server and apparently was busy at the time you were hitting it. ("503"= too busy to handle you)
I suspect that the WU was queued or possibly sent once the load on this CS became reasonable.
You should have been assigned a new WU to chomp on at some stage in the process.
I just looked at this server. Net load looks unusually high for what it is apparently doing.
