Fatal SQL error. Looks like you have duplicate hidden entries in _comprofiler_plugin_activity_hidden database table. It's not supposed to be possible for someone to hide an activity entry twice, but it might have happened on some occasions. The index for that table was made unique to improve its query performance and is what is causing your issue.
Suggest checking the _comprofiler_plugin_activity_hidden table and removing any duplicate rows. The below query can help find the duplicates.
Code:
SELECT `user_id`, `type`, `asset`, GROUP_CONCAT( `id` ) AS ids, COUNT(*) AS total
FROM `jos_comprofiler_plugin_activity_hidden`
WHERE `asset` IS NOT NULL
GROUP BY `user_id`, `type`, `asset`
HAVING total > 1;
Replace jos_ with whatever your table prefix is. Will see if I can find a away to improve the install script to find and get rid of the duplicates for you.