// Warning: Encountered a non-manifold vertex. Cannot Bevel. //
 

http://s1.directupload.net/images/130907/jlouqpuf.png

How to fix this Problem on those Edges?
EDIT: I did a clean mesh for manifold vertex-operation,now I can bevel. Problem solved! :beer:

Non manifold geometry is very bad and cleanup operations can be destructive so be careful.

Here are some examples of non-manifold geometry.
http://download.autodesk.com/us/maya...onmanifold.png