Comment 2 for bug 876268

I found the problem.

It was on /etc/apparmor.d/usr.sbin.mysqld , which clever unbuntu-bug found it was modified.

During upgrade, I was asked whether to substitute this file with a new version, but since I needed some of the current configuration and since I thought the changes where cosmetic (but they were not!), I choosed to keep my file.

I compared my file with the base version and applied the changes myself, and it worked. The changes were:

===
diff -u /etc/apparmor.d/usr.sbin.mysqld.bak /etc/apparmor.d/usr.sbin.mysqld
--- /etc/apparmor.d/usr.sbin.mysqld.bak 2011-10-17 10:02:03.000000000 +0200
+++ /etc/apparmor.d/usr.sbin.mysqld 2011-10-17 10:02:33.000000000 +0200
@@ -33,8 +33,8 @@
   /var/lib/mysql/** rwk,
   /var/log/mysql/ r,
   /var/log/mysql/* rw,
- /var/run/mysqld/mysqld.pid w,
- /var/run/mysqld/mysqld.sock w,
+ /{,var/}run/mysqld/mysqld.pid w,
+ /{,var/}run/mysqld/mysqld.sock w,

   /sys/devices/system/cpu/ r,
   /home/manolinux/.opentpv/** rw,
===

Sorry to disturb you, Ubuntu develpers, but I hope at least this report helps other people with similar problems.

Thanks.