by VanessaE » Wed Apr 10, 2013 05:59
This bug has happened on my server before, as well as a couple of other folks. At present, the cause is unidentified.
Workaround (either way may take up to several minutes to complete):
Using Worldedit, try selecting the area above, below, and around the shadow, for at least 20 nodes in the X and Z directions, at least 30 nodes below, and at least 100 nodes above. Use Worldedit's //fixlight command.
If that doesn't work, spawn a flat area of sand, desert sand, or gravel way above the shadowed area and wide enough to cover it completely, using Worldedit, then dig one any of the spawned nodes normally. This will cause the whole mass you spawned to fall down, which will force the engine to re-calculate light for the area. Let them fall, then use Worldedit's //replace command to swap out the gravel/etc for air. If you need to (and if it works at all), use /clearobjects to get rid of any stray floating blocks.
Good luck :-/