If you get the following error when upgrading your database, "Failed to update database to new version! Access to the path 'XXX' is denied.", please follow the following steps:
1) Exit out of Invoice Expert
2) Right click on the Invoice Expert icon
3) Select "Run as Administrator"
This should allow you to back-up/update the database and fix the permission denied issue. Once the database is upgraded, you are not required to "Run as Administrator" again.