I am also experiencing a similar problem with the RadComboBox.  My ComboBox contains a list of user names. A selected name is stored in the data text field and the user id is stored in the data value field. I am implementing a dynamic RadGrid since the number of columns can vary across the grid.  I am also implementing the grid in Batch edit mode at the cell level. I am using the item template to display the user name as a label and the edit item template to display the RadComboBox. When a user name is selected from the RadComboBox, the cell shows a red triangle to indicate an update has occurred and a Save is performed firing the BatchEditCommand event. The new values shows the new user id selected from the ComboBox and the adjacent columns on that row (which are the labels containing the user name) store an empty string in the user id field if the name contains all alpha characters. If the name contains a single quote or hyphen, then that character is stored to the user id field in new values.

Please see attached document.