User is getting an error when trying to edit some time entries.

It seems that the time entry was set to auto-approve, but security permissions did not grant rights to edit the approved entries. 

The Security Profiles screen enables you to create and customize security permissions for each user. CORE comes with a standard set of security profiles to get you started. However, you can customize an existing security profile and save that as a new profile. You can allow a user to edit time entries after they have been approved. That should resolve the issue.