Exploratorium appears to be down. MMB users will need to use the "Update Latest from JPL" option under the "Update" menu, instead of doing automatic updates, until Exploratorium is back up. I'll fix this in a future version - automatic updates should be able to just go on to JPL when Exploratorium is down.
In other news, a new minor release is coming up, with some nice performance improvements to the Slideshow feature. I've also 80% decided to go the GPL open source route, but we'll see.