If you have problems with Horde but SquirrelMail gives you the following message.
A fatal error has occurred Could not connect to database for SQL SessionHandler. Details have been logged for the administrator.
Here is what will fix the issue.
cd /tmp ls |grep mysql
If you see nothing after that then type the following
ln -s /var/lib/mysql/mysql.sock
You will probably want to run /scripts/upcp after this to make sure that it updates everything else.