There is a bug regarding the filtering of the grid, in the GridViewComboBoxColumn.
The filtering result displays wrong value.  
The bug accurse when:
   - Select a value form a GridViewComboBoxColumn.
   - Clear Filtering of the grid.
   - write a new value in the filtering GridViewComboBoxColumn cell, before living the cell.
The grid is filtered with the previous selected value.  
Note: the bug accurse only when the ReadOnly Property of column is off.