All OS -- I have an apple Macbook, a Linux box and a Windows 7. Error occurs on all machines.
2.69.11
I have an extremely detailed mesh, and I made a low poly mesh -- My thinking was, so long as I had them lined up (same scale, location, rotation) I could simply swap the mesh data from the high poly to the low poly and they would react the same way to the armature. Not the case.
Attached is a blend. On layer 1 is the armature and low poly mesh. Layer 2 has the high poly meshes. select the robotarmHP mesh. Change the mesh data to robotarmLP. bend the elbow (armature, right arm FK). The two meshes do not deform equally? It appears the vertex groups did not make the transition correctly.
Thanks
http://www.pasteall.org/blend/27661