For Leveller 2.5 and up to 2.6 alpha build 2604, there is a bug when
using selmasks and/or work areas with the "Tools->Affect Unbrushed Areas
Only" command.
Details: http://www.daylongraphics.com/products/leveller/issues.htm#0038
It has now been fixed for 2.6 following build 2604.
Ray