I think this is the way to go... this pertains directly to you I believe...
WARNING: If you received a refurbished LS670 from Sprint as a replacement, you might run into troubles trying to use the LG Mobile Support Tool to update to VC/VD. See this post for details on how to tell if you are affected by this problem. You can still revert to V9 and root. However if your refurbished unit is affected by this problem you will NOT be able to upgrade to the VC/VD using the LG Mobile Support Tool. You will need to force flash VC/VD using KP500. Instructions for how to do force flash VC/VD are in the reference section of this post.