M012: nnn unweighted vertices in Mesh [sss]
Secondlife needs all vertices of a rigged mesh to be assigned to at least one single weight. This message indicates that Avastar has found one or more vertices which do not have any weight. This is an error, Avastar will reject the export.
Note: You need to find the parts which have not been fully weighted and make sure every vertex has at least one weight assigned