th23 CMS love it but have issue - help !!!!!

[helen]

OK, I have followed all the instructions carefully but when I click "enabled" in the mods tab of the ACP it comes up with the following message. I think there are instructions that describe what to do when this happens at the bottom of the instructions but I can't follow them I'm afraid - complete newbie at mods here. Any help much appreciated. By the way I had a look at your site and love the way it looks. Hopefully I will be able to get my site looking just as neat and professional.

General Error
SQL ERROR [ mysql4 ]

Duplicate entry 'th23_cms' for key 1 [1062]

SQL

INSERT INTO phpbb_config (config_name, config_value, is_dynamic) VALUES ('th23_cms', 1, 0)

BACKTRACE

FILE: includes/db/mysql.php
LINE: 174
CALL: dbal_mysql->sql_error()

FILE: includes/functions.php
LINE: 157
CALL: dbal_mysql->sql_query()

FILE: includes/acp/acp_th23_cms.php
LINE: 1506
CALL: set_config()

FILE: includes/functions_module.php
LINE: 507
CALL: acp_th23_cms->main()

FILE: adm/index.php
LINE: 74
CALL: p_master->load_active()

[helen]

OK for some unknown reason that seems to have sorted itself out! But unnfortunately I now have a different error message and I have no idea of how to fix it.

"Fatal error: Call to undefined function: cal_days_in_month() in /share/storage/03/mi/michaeldinning/phpBB3/includes/th23_cms.php on line 623"

I have found the file and the line where the error occurs but dont know how to fix it. Can anyone help at all? I really need this mod to make my site work. Either that or I'm going to have to undo everything i did when installing this MOD and that sems a pity seeing as I'm so close to getting it to work.