System Information
Windows 7 64, HD 5770

Blender Version
Broken: 9337574 (2.71 release) + c670ceb

Short description of error
Curve modifiers vertexgroup option to determine the influence doesnt work when the modifier is used on a lattice.

Exact steps for others to reproduce the error

(There is a bone to check if it works at all)

• Add a Curve.
• Add a Lattice.
  • Give it a new vertex group (=Group).
  • Assign it partially on Lattices mesh.
• Give Lattice a Curve modifier.
  • Use Curve.
  • Use the new vertex group (Group) as Influence group in the modifier.

Problem: The whole lattice gets deformed, no matter if vertices belong to the group or not.