application will not allow edit of existing data on certain customers >>SQL Server 2012 Express

I am using a business management software application that uses SQL Server 2012 for data storage.  The application is one that stores data about the customer, and then displays as requested. On certain customers, once saved, no save of future edits will work.  Once the save button is clicked, there is a momentary hula hoop, followed by nothing. You have to cancel to get out, and then going back you see that the data was not saved. This only happens on certain customers (however, once the problem develops for a certain customer, it is consistent) and newly created customers seem to work fine.  I am thinking that the software app is fine since the save process would be the same each time the button was clicked, so I am thinking its a database problem.  Any thoughts or direction would be greatly appreciated.