I upgraded our site two days ago (update to InnoDB engine included) and everything went perfectly - some excellent new features (thanks devs!). Today I tried to delete a resource and recieved an 'error/backup_check_user_not_exists' error popup. I've done a bit of testing and it seems to be the same sitewide.
A quick check of backup/util/checks/backup_check.class.php and backup/util/checks/tests/checks_test.php suggest that this error is thrown after a check that userid must exist in user table which of course it does since I'm logged in!
Any ideas would be most appreciated.