Question:
Why does a user receive the following error: Insufficient Privileges? This error occurs when the user tries to access the Sharing Detail page of a record.
Answer:
This is the anticipated outcome if the record's object sharing setting is either set to public read/write or controlled by parent.
When using public read/write, the record is available for every user.
When using controlled by parent, the record access is controlled by the parent record.
Related Documentation:
CRM Help Article: How to Determine Why a User Has Access to a Record in Salesforce.com (SFDC)?