You can receive such errors in case you have specified the DataAccessKindAttribute as 'ReadOnly'. Please see this link
To fix it, please review the setting for the particular field and set it to 'ReadWrite'
I hope this information is helpful for you.
Do come back in case you need further information.
OpenAccess ORM is now Telerik Data Access
. For more information on the new names, please, check out the Telerik Product Map