>Peter suggests to check the indexes (if any index includes this field).
>
>You can check indexes using
>sp_HelpIndex SP.
>
>In addition, the field can be used in Check constraint.

You may say thanks to him. But, I believe it goes back to what I was saying earlier on today. I see some items in Constraints. When I removed them all, I was able to run the script. I believe the DEFAULT WITH VALUES clauses add item in the constraint list.

So, basically, I will have to adjust my script to remove all the constraint related to the field I need to remove before executing the ALTER TABLE DROP COLUMN line.

I also found it quite confusing that when we remove a constraint manually from SSMS that it doesn't get removed. It is, but we have to force a refresh to get the updated list.