Haven't seen a fix for this anywhere else so don't flame me if there is one... some random easter egg/mistake...
http://i774.photobucket.com/albums/yy30/Chainy3672/Misc/before.jpg
http://i774.photobucket.com/albums/yy30/Chainy3672/Misc/After.jpg
Clean simple esp fix:
http://www.4shared.com/file/c4k9UvDt/Black_Mark_Fix.html
Edit: 2 cells fixed now, extra thanks to papill6n for spotting one.
Cells fixed:
(-18, 28)
(-27, 27)
If you don't have Bloodmoon, you dont need this fix.
If you have Bloodmoon, you can probably live without this fix.
Plugin requires Bloodmoon only.