Hi Hanung,

I have had issues with importing and exporting weights as well. Hopefully you still have a file of the skinned mesh. If so, this is what I found works best...

1. Skin your character to your updated rig
2. Reference the file containing your old skinned character into the scene with the updated rig
3. Select the old skinned character and the new skinned character, in that order.
4. Make sure to leave both rigs in the same position
5. Go Under Skin>Edit Smooth Skin>Copy Skin Weights>Option Box
6. In the options, reset the settings to the defaults, then hit Copy.
7. Check to make sure that the new skinned character has the proper weights
8. Go back to the Reference Editor and remove the referenced file that contained the old rig.

If you have only made minor tweaks to the positions of the joints and/or mesh, you shouldn't have to do too much fixing of the weights.

Hope that works for you. It might also be worth looking into seeing if there are other scripts that do a better job of transferring weights than the default Maya ones.

-Dustin

wow Amazingly it works well Dustin.. Thank you for your advise. ^ ^

That's great, good thing you kept a back-up file. I don't know why the import/export doesn't work better... I have had some success with it, and sometimes not so much.