The hosted environment for Blackbaud NetCommunity is set up to give an error message indicating to users that the site is under maintenace. However, because of the way that the notification message works, it doesn't always display. If your site is hosted by Blackbaud, then it is on two redundant servers (nodes). A netscaler is used to balance traffic between the two servers. If that device detects that both nodes are down, then it displays that error page automatically. However, upgrades in the hosted environment are often finished before the netscaler detects that both nodes are down. If this happens, the "friendly" error message will not be displayed.