The 20090822 map maker released today handles map darkness slightly differently from, and is therefore incompatible with, previous releases.
Well actually it's not that black and white. The nitty-gritty is here:
http://www.daimonin.org/forums/daimonin-project/map-darkness-setting/So you'll want to double check your existing maps to make sure darkness is properly set.
This is simple. In Gridarta, load the map file and open the properties window. Check the darkness field:

0 means total darkness, 1 to 7 are decreasing levels of darkness, -1 means server default (which ATM is 7).
Basically in previous releases Gridarta would say 0 but the server would interpret this as -1 (so 7). This meant that Gridarta could not produce total dark maps. Now, 0 means 0.
So you need to make sure that your maps have the actual darkness setting you mean.
For outdoors maps (which have variable lighting over the course of a day_, darkness is the maximum ambient light level. So a darkness 4 outdoors map will never get very bright even at midday. For outdoors maps darkness 0 makes no sense then so this will be ignored.
Lippy has already upgraded all the maps on the SVNs (ie, the Map Wizard's maps and all the official maps) and the dev server is rebuilt.
So Map Wizards should be sure to update their maps to the latest SVN before committing anything.
For mappers whose maps are not on SVN, you'll need to edit the darkness on existing maps as above to be sure before your maps will work properly. New maps, generated by 20090822 will be fine.