Ubuntu 11.10 -> 12.04 upgrade wipes all mysql databases and user info

Package: mysql-server (and possibly other mysql-related packages)

Upgraded by using 12.04 LiveCD, 64-bit version. On completion of apparently successful upgrade, all user mysql databases are GONE from /var/lib/mysql/. All user account information seems to be gone, according to Workbench. Unable to log into PHPMyAdmin by any means. It looks like the upgrade completly deletes all previous mysql data and does a fresh install.

This is some seriously unfriendly behavior that, if not just a fluke, warrants immediate attention.

ProblemType: Bug
DistroRelease: Ubuntu 12.04
Package: mysql-server 5.5.22-0ubuntu1
ProcVersionSignature: Ubuntu 3.2.0-24.37-generic 3.2.14
Uname: Linux 3.2.0-24-generic x86_64
NonfreeKernelModules: wl
ApportVersion: 2.0.1-0ubuntu7
Architecture: amd64
Date: Sat Apr 28 08:45:10 2012
InstallationMedia: Ubuntu 12.04 LTS "Precise Pangolin" - Release amd64 (20120425)
Logs.var.log.daemon.log:

Logs.var.log.kern.log:
 Apr 27 16:25:49 warren-laptop2 kernel: [ 21.905012] type=1400 audit(1335569149.398:19): apparmor="STATUS" operation="profile_load" name="/usr/sbin/mysqld" pid=957 comm="apparmor_parser"
 Apr 27 16:25:49 warren-laptop2 kernel: [ 21.962907] type=1400 audit(1335569149.454:20): apparmor="STATUS" operation="profile_load" name="/usr/sbin/mysqld-akonadi" pid=958 comm="apparmor_parser"
 Apr 27 22:11:29 warren-laptop2 kernel: [ 8.041361] type=1400 audit(1335589889.165:11): apparmor="STATUS" operation="profile_load" name="/usr/sbin/mysqld" pid=914 comm="apparmor_parser"
 Apr 28 07:15:50 warren-laptop2 kernel: [ 2060.905423] type=1400 audit(1335622550.652:28): apparmor="STATUS" operation="profile_replace" name="/usr/sbin/mysqld" pid=6353 comm="apparmor_parser"
 Apr 28 08:30:10 warren-laptop2 kernel: [ 6514.017884] type=1400 audit(1335627010.736:30): apparmor="STATUS" operation="profile_replace" name="/usr/sbin/mysqld" pid=11966 comm="apparmor_parser"
MySQLConf.etc.mysql.conf.d.mysqld.safe.syslog.cnf:
 [mysqld_safe]
 syslog
MySQLVarLibDirListing: False
PackageArchitecture: all
ProcEnviron:
 TERM=xterm
 PATH=(custom, user)
 LANG=en_US.UTF-8
 SHELL=/bin/bash
SourcePackage: mysql-5.5
UpgradeStatus: No upgrade log present (probably fresh install)