There is a post on the Grid Status page. It gives a bit different spin to Thursday’s down time than what I heard. Whatever, there will more work done to fix some things on Monday and that work may take SL offline for a time Monday morning.
[UPDATED 2:30pm PDT, 27 April 2012] On April 26, 2012, the Second Life engineering team was performing an upgrade to the core network. The upgrade triggered a bug that led to downtime and instability throughout the day. The maintenance described in this post is scheduled for Monday, April 30 at 6am PT in order to correct the bug and may result in additional service interruption. We apologize for the service disruption and appreciate everyone’s patience. [POSTED 1:00pm PDT, 27 April 2012] We will be performing scheduled maintenance Monday April 30, 2012 beginning at 6:00am until approximately 9:00am. Please save all builds and refrain from rezzing no copy objects or making inworld L$ transactions. Some residents may experience delays logging inworld. Please follow this blog for any updated information.