Hi Trevor,
Thank you for contacting Clarizen Support. Let me ask you few questions to help us narrow down the issue:
1) Which date changes automatically when you report Actual Effort? Is it Actual Start Date?
2) Are you updating Actual Effort _manually or is _Actual Effort updated from timesheet?
3) Can you verify if you have installed any of the following applications (Settings >> Configure) ?
a) Set Actual Start Date
b) _Set Actual Start Date upon insertion of timesheet
_Thank you,
Diana