When you add a quote you cannot delete it until you refresh the page - so if you add something in error you have to refresh before you can delete.
Confirmed in master.
This is probably fixed by bug 12163. Please test and update the status accordingly.
In Firefox I still cannot select a quote I have just added to delete it - I have to refresh the page.
This looks to be very similar or a duplicate of bug 8797.
*** This bug has been marked as a duplicate of bug 8797 ***