IEEE have notified us about scheduled maintenance for their site (purple text indicates NZ time):

On Monday, May 23rd, 2016, we will be moving the IEEE Xplore service from our backup facility to the New Jersey Data Center.

IEEE Xplore will be unavailable on Monday, May 23rd, 2016, for approximately 1 hour starting at 1:00pm Eastern Time. (New York)  = 5-6 am Tuesday 24th May in NZ

and

users may experience intermittent issues from 2:00pm – 6:00pm ET ( 6-10 am Tuesday 24th May in NZ)

These types of moves are typically transparent to all of our customers. No action is required by the vast majority of our customers and your IEEE Xplore access should be unaffected by this change.