Thanks Nabeel. 
This is what I am getting.... 
Backtrace: DB::write_debug > DB::query > PilotData::SaveFields > PilotAdmin->viewpilots > call_user_func_array > MainController::RunAllActions 
Query: INSERT INTO phpvms_fieldvalues (fieldid, pilotid, value) VALUES (2, 1, '1234567') 
Error: (1452) - Cannot add or update a child row: a foreign key constraint fails (`mysite/phpvms_fieldvalues`, CONSTRAINT `phpvms_fieldvalues_ibfk_2` FOREIGN KEY (`pilotid`) REFERENCES `phpvms_zzzz` (`pilotid`) ON DELETE CASCADE) 
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The thing is phpvms_zzzz doesn't exist.  I believe it was a table used early on to replicate the pilots table but since has been deleted.