Upgrade to 1.1.21 PHP Warning: Module 'mysqlnd' already loaded in Unknown on line 0

Hi all,
I've upgrade to 1.1.21 and I'm getting this email. I found a post about this in German but my German is not good enough to translate it. Is it a symbolic link problem or something?

Thanks,
Rob

Thanks guys..

Hi guys,
I still have problems receiving loads of notification emails with this error:

PHP Warning: Module 'PDO' already loaded in Unknown on line 0

I have these files in my /etc/php5/conf.d/

root@sosaria:/etc/php5/conf.d# ls -alF
total 12
drwxr-xr-x 2 root root 4096 Jan 18 23:02 ./
drwxr-xr-x 6 root root 4096 Apr 11 2014 ../
lrwxrwxrwx 1 root root 29 Apr 11 2014 10-mysqlnd.ini -> ../mods-available/mysqlnd.ini
lrwxrwxrwx 1 root root 25 Apr 11 2014 10-pdo.ini -> ../mods-available/pdo.ini
lrwxrwxrwx 1 root root 26 Apr 11 2014 20-curl.ini -> ../mods-available/curl.ini
lrwxrwxrwx 1 root root 24 Apr 11 2014 20-gd.ini -> ../mods-available/gd.ini
lrwxrwxrwx 1 root root 26 Apr 11 2014 20-imap.ini -> ../mods-available/imap.ini
lrwxrwxrwx 1 root root 26 Apr 11 2014 20-intl.ini -> ../mods-available/intl.ini
lrwxrwxrwx 1 root root 28 Apr 11 2014 20-mcrypt.ini -> ../mods-available/mcrypt.ini
lrwxrwxrwx 1 root root 28 Apr 11 2014 20-mysqli.ini -> ../mods-available/mysqli.ini
lrwxrwxrwx 1 root root 27 Apr 11 2014 20-mysql.ini -> ../mods-available/mysql.ini
lrwxrwxrwx 1 root root 25 Jan 9 15:56 20-pdo.ini -> ../mods-available/pdo.ini
lrwxrwxrwx 1 root root 31 Apr 11 2014 20-pdo_mysql.ini -> ../mods-available/pdo_mysql.ini
-rw-r--r-- 1 root root 56 Mar 14 2010 adodb.ini
root@sosaria:/etc/php5/conf.d#

@TheCry
Should I remove the 20-pdo.ini -> ../mods-available/pdo.ini link too?
I'm an admin

Will the installer reinstall PHP5?