DataGridView ComboBox Key Press/Down Event takes 1-2 seconds to fire

Hi,
I have a combo box column in a datagridview. In this column, I have several values that starts with the same letter
For Eg: DA, DB, DC, DE, DF, DG..etc.
While using a normal combo box control, I can easily navigate through values by just pressing "D". It will take me through all items that starts with "D".
Now, In the datagrieview, when I try to do this, the grid only accepts my first "D" click. It ignores subsequest clicks if I do it faster. But if I wait for 1-2 seconds and press "D" again, then it works fine. Any ideas on how to fix it.
The response time of overall process is getting hit by this single delay as the customers now have to either wait 1-2 seconds or use down arrow and scroll through..
 
Thanks
Paul