Kristen,
At risk:
There's a 10% tolerance between Expected Progress (a linear calculation of work/duration of a task) and actual %complete.
http://usermanual.clarizen.com/#scheduling-status
Off track:
Passed Due date - calculated by a nightly job (midnight).
Actual Effort/Work * 100 gives you % Completed
As for your Expected Work comment, there is no such field, I believe you are referring to Work. Work typically is not Locked unless you are looking at the higher work item levels. Understand that any fields that are 'Roll Up' fields, meaning that the data gets rolled up from Sub-Items (i.e. Milestones, Tasks and Sub-Tasks), these will always be locked and can only be modified at the lowest level (i.e. Task or Sub-Task). Any changes will then roll up all the way to the Project level and cannot be changed there. That is why it is locked. You will see this in a number of fields.
Sincerely,
Boris Krutiy