Can't rename vertex groups

In some of the objects I am working on, I cannot rename the vertex groups from “Group” or “Group.001” when I double click on the word “Group” nothing happens.

Puzzled, as a test, I made a cube, went into edit mode and selected some vertices, created a group and renamed it, no problem.

Is there some kind of a switch somewhere that locks the vertex group names?

Thanks.

Well, I found a work around.

I made a new file, I appended the object into the file. Blender brought the armature it was childed to as well. I undid the parenting and then found I could rename the Vertex Group. I did, saved the file as a different name. Then I opened the original file, deleted the object and then appended the modified object into the file and childed it to the armature.