--- Operating System, Graphics card ---
Ubuntu 12.04 - Nvidia 8600

--- Blender version with error, and version that worked ---
r60988

--- Short description of error ---
if I remove the vertex group mask modifier is not updated correctly, it looks as if he had not deleted the vertex group

--- Steps for others to reproduce the error (preferably based on attached .blend file) ---
1. Add a Cube.
2. Select the Cube, enter in edit mode, select 4 vertex and add a vertex group. Enter in mode object.
3. Select the Cube and add a Mask modifier.
4. In the Mask modifier with Vertex mode, add the vertex group.
5. In the Mask modifier, remove the vertex group previously added.

Watch video adjunt