Thursday morning (11/7) starting about 7 AM PDT Second Life™ will sort of be down. The Lindens will be doing some database maintenance. They will have the following impacts:

During this period, a number of Second Life services will be impacted. Some users may be logged off and may be temporarily unable to log in for a brief period. The maintenance may also disrupt transactions, logins, and account registration. The land store and land auctions may also become unavailable during this time. 

Of course, it is unwise to rez no-copy items, attempt financial transactions, or modifying Market Place entries. Trying to build or script in SL will likely be flakey too.

You can see the post here: Expected Downtime Thursday, November 7. They say they will update the post when the maintenance is complete.