MF> So this still is broken. Basically, sign in as a new user and once the
 MF> user is validated to the new security level with a different menu
 MF> assigned, the menu never gets assigned. So once the user tries to login
 MF> again he will get a 'Error loading .mnu'
 MF> 
 MF> When checking the user, the Start Menu is empty.

The start menu is no longer copied to the user's record like it used to be when a user is upgraded so that part is normal.  Instead, it now pulls the menu name from their security level and has some different logic.  There is a note about this in the whatsnew for more details.

I'll try to reproduce it here tonight if I get the time.

If you want to diagnose more on your side, here are some things to try:

1) Check logs to see what it says when it can't load the menu.
2) Check system config > start menu and confirm the value is what you want
3) Check the user's start menu and make sure its actually blank and not a null
4) Check the user's security level to make sure there is a start menu defined or that its truly blank and not set to a space or null character.

The logic is basically:

If user has a non-blank start menu, use that.
If user start menu is blank, then load menu from user's security profile.
If user security profile start menu is blank, then load Config > Start Menu

... Enter any 12-digit prime number to continue.

--- Mystic BBS v1.12 A48 (Windows/64)