inMesh plug being written incorrectly

[vince touache]

howdy, 

I'm fighting against what seems to be a bug, I'd like to know if anyone else faced the same thing before

Custom node, with a mesh attribute (MFnMeshData::kMesh), storable. 

I connect a mesh plug to it in maya, refresh, disconnect, and save as *.ma

If I open my scene with a text editor, I get the right information into the mesh attribute, that is, vertices, edges, etc.... I also get other keys that I don't know: "left", "bottom", "right", and I have no idea what they do. 

Now my problem is that some of my custom nodes, when I save, get written incorrectly. Therefore, when I re-open my scene, maya fails to set my mesh attribute back to what it was when I saved. Specifically, with a correct file, I have something like

    setAttr "myAttributeName" [...]

        "left" 0

        "bottom" 0

        etc...

and with a corrupted file, I just have the key, and no value: 

    setAttr "myAttributeName" [...]

        "left"

        "bottom"

        etc...

So from there, I have 2 questions:

• what on earth are those "left" "bottom" "right" ... keys/values inside a mesh attribute and what are they used for?
• what could cause maya to not write my mesh attribute correctly when I save my scene?

The problem seems to exist only with *.ma, not *.mb

Any help would be appreciated!

Thank you