FIX. RadGridView - cannot show tooltips in GridViewComboBoxColumn, while in RadDropDownList the tooltips work correctly
This item has been resolved in Q1 2014 - have a look at its status. You should upgrade to the latest version in order to take advantage of the fix. If you are using earlier version, please contact our support team with the precise case you have and they will check if a suitable solution exists.
i am facing same issue, so not sure is issue is fixed, any one could provide sample code for GridViewComboBoxColumn.