Neil,
I realize I need to add some upgrade documentation to the online help or right in the member area. Up until now I have been including instructions with the update email. (Which I didn't release for v1.77b)
Standard upgrade procedure is as follows:
1. Simply replace all of the files in your main ListMail folder, except config.php with the new ones.
2. Re-login to the program so that any required database changes can take effect.
With v1.77b you need to relogin to the program not because the database has changed, but because the login process has changed.
Regards