Taken from the Second Life Grid Status page.
[Posted 9:45am PDT, 8 May 2012] We [Linden Lab] will be performing scheduled maintenance [on the Second Life system] today, Wednesday and Thursday of this week (May 8, May 9, May 10), beginning at 6:00pm PDT each day. Each maintenance is scheduled to last around 8 hours. Please save all builds and refrain from rezzing no copy objects, as some regions may be taken offline and remain offline for extended periods of time. Please follow this blog [Grid Status blog] for any updated information.
See the coming SL News post for some speculation and ideas to what is going on.
Spikes, Slow Restarts For Some Regions Overnight
[Posted 9:25 pm PDT, 07 May 2012]
Some regions are taking longer than normal to work their way through restarts this evening. In addition, they’re reporting higher-than-normal spikes in performance and viewer instability.
Our engineers have done the preliminary work tracing the problem and will be forming a team early tomorrow to fully diagnose and correct it.
Tonight, please file a “region offline” service request as needed for any region which remains inaccessible to you for longer than 15 minutes or so, and we’ll work with our network engineers to assist the restarts as needed.