Paul,
If there was only the updated Navdata on the computer it would be being read correctly, there must be another on there if only 80,000 codes are being read. If all the original files had been deleted there would only be the updated on there, hence my suggestion to carry out a windows search for Navdata.db3 files.
Carrying out a de-installation using the Windows control panel does not remove all files and normally leaves the original Navdata.Db3 file among others.
Alan