Update to 11.10 - phpMySql update stuck if root@localhost has password set

[Stephan]

On updating from 11.04 to 11.10 the updater got stuck in an infinite loop trying to access MySQL as root without password.
Workaround: Unsetting MySQL's root password.

Fragment from output to terminal:

ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)
dbconfig-common: phpmyadmin configure: retrying.
dbconfig-common: writing config to /etc/dbconfig-common/phpmyadmin.conf
Replacing config file /etc/phpmyadmin/config-db.php with new version
creating database backup in /var/cache/dbconfig-common/backups/phpmyadmin_4:3.3.10-1.mysql.
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO).
unable to connect to mysql server.
error encountered backing up the old database:
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)
dbconfig-common: phpmyadmin configure: retrying.
dbconfig-common: writing config to /etc/dbconfig-common/phpmyadmin.conf
creating database backup in /var/cache/dbconfig-common/backups/phpmyadmin_4:3.3.10-1.mysql.
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO).
unable to connect to mysql server.
error encountered backing up the old database:
ERROR 1045 (28000): Access denied for user 'root'@'localhost' (using password: NO)
dbconfig-common: phpmyadmin configure: retrying.

ProblemType: Bug
DistroRelease: Ubuntu 11.10
Package: xorg 1:7.6+7ubuntu7
ProcVersionSignature: Ubuntu 2.6.38-11.50-generic 2.6.38.8
Uname: Linux 2.6.38-11-generic x86_64
ApportVersion: 1.23-0ubuntu3
Architecture: amd64
Date: Thu Oct 13 22:39:57 2011
EcryptfsInUse: Yes
ProcEnviron:
 LANGUAGE=
 PATH=(custom, user)
 LANG=de_DE.UTF-8
 SHELL=/bin/bash
SourcePackage: phpmyadmin
Symptom:
UpgradeStatus: Upgraded to oneiric on 2011-10-13 (0 days ago)