Column drop-down menu not functioning

I had added an extra column called 'Comment' and it had a drop down menu that said 'On Kindle' so I could keep track of what was on my device. I downloaded Calibre ver. 2.64.0 and suddenly the drop-down menu doesn't work. The column is still visible but when I click it it's blank.

In version 2.63.0 I could simply click on the 'Comment' and the 'On Kindle' would appear as a selection. Now it doesn't; so if I want to use it I have to type in the words each time. What happened? :(