The NASA World Wind Servers will be down for maintenance this weekend, this means unless you have your data cached locally you won’t get any imagery, for .NET you will also experience long load times and possibly no toolbar, for Java apps I’m not quite sure what problems will occur.
The WorldWind Central server will still be up so any data, such as Zoomit!, that is served by us should still work, the Virtual Earth plug-in for .NET should also still work, but Java’s will not.