Logon to admin and activate debugging in settings and you should be able to see the error either as part of the screen where the module would be or in the footer.
B: But I can't login to admin because of the error
try this instead...
open config.php and turn debugging to true
PHP:
define('CPG_DEBUG', true);
then go to phpmyadmin:
Code::
UPDATE `cms_config_custom` SET `cfg_value`='1546' WHERE `cfg_name` = 'debug' AND `cfg_field` = 'error_level';
then delete config_MAIN_CFG.php from cache dir of dragonfly
It is often simply an errant block that is the problem, so use this to access blocks admin,
admin.php?op=blocks&hideallblocks=1
This will hide the blocks and allow you to de-activate individual blocks.