That probably means that your view center point was set to far off, distant places for which you did not have maps downloaded. (I think the default is somewhere on the equator.) Centering onto the "current location" (which you can also do via the "Enter" key, by the way) would bring you back to a sane location, assuming you have a GPS receiver.

Still, if you had auto-download enabled, it would have downloaded any needed maps for you, unless maybe you were using a repository that doesn't have maps near the equator.

Anyway, sorry for the trouble!