I'd use a work-around. Copy the mail from the inbox to a new folder you make in Windows mail. Then migrate. Then copy back in Windows Live Mail.
Success seems guaranteed if any other folder than the Inbox transfers OK.
A friend bought his wife a new Windows 7 laptop. He is now transferring files from her old Vista desktop. On the old machine she used Windows Mail and on the new machine plans to use Windows Live Mail. He asked for help in migrating the mail-related files.
Moving the Contacts was easy. I then exported the messages from Windows Mail in Windows Mail format to a new folder on the desktop. I copied that folder to the desktop of the new machine and imported from Windows Mail format from that folder.
The process put everything into an Imported folder and in that folder are all her message folders. Each folder looks fine in Windows Live Mail except the InBox. There are messages in the InBox with blank info and when you open any of those messages they are blank. The messages in the other folders appear fine. Any help would be appreciated.
The friend's wife has been in the hospital for a while and they are hoping to get her home this weekend. He wants to surprise her with the new computer.