Hello,
I actually just ran into this issue. I ran into the issue after I went to the Human Resources Preferences window and activated an Employee Filter by Department.
I tried to clear the Employee Filter to see if the error message will go away, but that did not resolve the issue. I found that the settings were stored in the DYNAMICS..SUSPREF table. I cleared out the table and the error message stopped popping up. Incidentally, the system stopped asking for a Reason when I saved changes on the Pay Code.
I went to the Human Resources Preferences window again and saw that the "Enable Reason for Pay Adjustment" was already checked (strange, as I had cleared the table). I clicked OK and attempted to Save the Pay Code record again. And the error message popped back up.
I again cleared the table and only added a handful of records back. This seemed to do the trick, but if I open the window and Click OK on it or make changes to the Human Resources Preferences window I get the error again.