If you are getting horde session handler error, then please check if horde db is present on server or not. You can use following steps.
#mysqlshow |grep horde
It should give you output like,
[~]#mysqlshow |grep horde
| horde |
If the output is blank, then you need to create a db called horde.
You can do it with commnd.
#mysqladmin create horde
Then run a script :
If horde db is already exist on server then go to mysql and on mysql prompt run commands.
mysql>repair table horde_sessionhandler;
Then on shell prompt run commands
It will fix the most of issue with horde.