$ sudo aptitude install mysql-server
Reading package lists... Done
Building dependency tree
Reading state information... Done
Reading extended state information
Initializing package states... Done
The following NEW packages will be installed:
  libhtml-template-perl{a} mysql-server mysql-server-5.0{a} mysql-server-core-5.0{a}
0 packages upgraded, 4 newly installed, 0 to remove and 12 not upgraded.
Need to get 0B/27.7MB of archives. After unpacking 91.1MB will be used.
Do you want to continue? [Y/n/?] y
Writing extended state information... Done
Preconfiguring packages ...
Selecting previously deselected package mysql-server-core-5.0.
(Reading database ... 17022 files and directories currently installed.)
Unpacking mysql-server-core-5.0 (from .../mysql-server-core-5.0_5.1.30really5.0.75-0ubuntu10.3_amd64.deb) ...
Selecting previously deselected package mysql-server-5.0.
Unpacking mysql-server-5.0 (from .../mysql-server-5.0_5.1.30really5.0.75-0ubuntu10.3_amd64.deb) ...
Selecting previously deselected package libhtml-template-perl.
Unpacking libhtml-template-perl (from .../libhtml-template-perl_2.9-1_all.deb) ...
Selecting previously deselected package mysql-server.
Unpacking mysql-server (from .../mysql-server_5.1.30really5.0.75-0ubuntu10.3_all.deb) ...
Setting up mysql-server-core-5.0 (5.1.30really5.0.75-0ubuntu10.3) ...
Setting up mysql-server-5.0 (5.1.30really5.0.75-0ubuntu10.3) ...
 * Stopping MySQL database server mysqld                                                                                                                                                         [ OK ]
/var/lib/dpkg/info/mysql-server-5.0.postinst: line 144: /etc/mysql/conf.d/old_passwords.cnf: No such file or directory
dpkg: error processing mysql-server-5.0 (--configure):
 subprocess post-installation script returned error exit status 1
Setting up libhtml-template-perl (2.9-1) ...
dpkg: dependency problems prevent configuration of mysql-server:
 mysql-server depends on mysql-server-5.0; however:
  Package mysql-server-5.0 is not configured yet.
dpkg: error processing mysql-server (--configure):
 dependency problems - leaving unconfigured
No apport report written because the error message indicates its a followup error from a previous failure.
                                                                                                          Errors were encountered while processing:
 mysql-server-5.0
 mysql-server
E: Sub-process /usr/bin/dpkg returned an error code (1)
A package failed to install.  Trying to recover:
Setting up mysql-server-5.0 (5.1.30really5.0.75-0ubuntu10.3) ...
 * Stopping MySQL database server mysqld                                                                                                                                                         [ OK ]
/var/lib/dpkg/info/mysql-server-5.0.postinst: line 144: /etc/mysql/conf.d/old_passwords.cnf: No such file or directory
dpkg: error processing mysql-server-5.0 (--configure):
 subprocess post-installation script returned error exit status 1
dpkg: dependency problems prevent configuration of mysql-server:
 mysql-server depends on mysql-server-5.0; however:
  Package mysql-server-5.0 is not configured yet.
dpkg: error processing mysql-server (--configure):
 dependency problems - leaving unconfigured
Errors were encountered while processing:
 mysql-server-5.0
 mysql-server
Reading package lists... Done
Building dependency tree
Reading state information... Done
Reading extended state information
Initializing package states... Done
Writing extended state information... Done

Before I installed it, I ran this:

sudo aptitude purge mysql-server mysql-server-5.0

This has happened before. I remember before, I did something with dpkg with fixed it.