Using Chrome and Safari, I noticed that under Who? if "a specific user" is selected the users drop down box doesn't appear until the previous drop down box i.e. "a specific user" is clicked another time. I tried completing the permission without selecting the user, it went ahead and the last selected user.

Similarly, if I were to select "a specific user" and by clicking it another time select the user and change my earlier selection to anything other than "a specific user" the user name doesn't disappear until I click the previous drop down box again.

However, above bug is not reproduced using an IE!