[Typo3] BE admin login not working after upgrade

[Jane Larsen]

I have tried an upgrade from 3.7.1 to 3.8.0
After copying files and working a little with the DB analyzer it was time to 
check the backend (frontend was ok)...

I cant login anymore! I've tried the standard login, the login I used before 
upgrading and even tried to set a new admin user from the DB analyxer in the 
install tool but no luck so far...

Any ideas as to how I gain access again?

//Jane Larsen