We finally figured out the problem, the field was a NEW field added to the table after the table was created.  So the existing records had the value set to DBNull in the table.  It looks like the control can't handle the condition where the value is DBNull.  The script to populate that field in the database wasn't run, in the database where it was being tested.

Actually the CheckBox is NOT disabled, I can click the checkbox and it is unchecked, and I and click on it and it is Checked and Black.  I want to allow the user to be able to edit the field,

I'm not allowing the user to edit all the fields in the grid, so I have the CellActivation for those controls set to Activation.NoEdit.

I added the following line of code even though I didn't need to do it because I can check and Uncheck that column.

columns[“Active_Flag”].CellActivation = Activation.AllowEdit;

so you can see after InitializeLayout code the CheckBox is greyed out, I click the control to uncheck I notice the pencil, then I recheck and the button is checked again. 

Whatever that pencil indicator is seems to be what's causing the issue I'm having. 

BTW thank you for your code but it wasn't useful to me.

Note I have no other events the are being fired for that grid that could interfere with this.