Thank you for the details Eric,
I was able to successfully import tes11.xls as non-tagged data. Export/Import with alternate tag works fine as well.
Could you try to create new project, create alternate T-N tag and try to import test11.xls. This will let to determine if this is project specific or not.
As well could you please pack projdata.mdb and upload it, i would like to review it.
Thanks,
Artiom