We just reviewed the database of a customer who was experiencing a similar problem. In their case the issue was caused by missing data. The issue was resolved by running the following query:
--BEGIN QUERY
EXEC ckbx_Install_AddItemFormatter 'Captcha', 'Text', 'Checkbox.Web.Forms.Items.Formatters.CaptchaItemFo rmatter', 'Checkbox.Web'
GO
EXEC ckbx_Install_AddItemFormatter 'HiddenItem', 'Text', 'Checkbox.Web.Forms.Items.Formatters.HiddenItemFor matter', 'Checkbox.Web'
GO
EXEC ckbx_Install_AddItemFormatter 'Checkboxes', 'Text', 'Checkbox.Web.Forms.Items.Formatters.SelectManyIte mFormatter', 'Checkbox.Web'
GO
EXEC ckbx_Install_AddItemFormatter 'DropdownList', 'Text', 'Checkbox.Web.Forms.Items.Formatters.Select1ItemFo rmatter', 'Checkbox.Web'
GO
EXEC ckbx_Install_AddItemFormatter 'RadioButtons', 'Text', 'Checkbox.Web.Forms.Items.Formatters.Select1ItemFo rmatter', 'Checkbox.Web'
GO
EXEC ckbx_Install_AddItemFormatter 'SingleLineText', 'Text', 'Checkbox.Web.Forms.Items.Formatters.SingleLineTex tBoxItemFormatter', 'Checkbox.Web'
GO
EXEC ckbx_Install_AddItemFormatter 'RadioButtonScale', 'Text', 'Checkbox.Web.Forms.Items.Formatters.RatingScaleIt emFormatter', 'Checkbox.Web'
GO
EXEC ckbx_Install_AddItemFormatter 'MultiLineText', 'Text', 'Checkbox.Web.Forms.Items.Formatters.MultiLineText BoxItemFormatter', 'Checkbox.Web'
GO
EXEC ckbx_Install_AddItemFormatter 'FileUpload', 'Text', 'Checkbox.Web.Forms.Items.Formatters.UploadItemFor matter', 'Checkbox.Web'
GO
EXEC ckbx_Install_AddItemFormatter 'Matrix', 'Text', 'Checkbox.Web.Forms.Items.Formatters.MatrixItemFor matter', 'Checkbox.Web'
GO
--END QUERY
You will need to restart IIS before in order to complete the change. If this does not resolve your issue I would suggest contacting the support team. You can either open an online ticket (
Checkbox - Login To Customer Area) or a phone support incident (
Checkbox Support - Phone Support).