This is a minor thing, but it drives me crazy.
As an example:
1. Select a changeset from the History page 2. Click 'Cases' in order to assign a case to the changeset 3. Start typing the case number
A dropdown box will appear with the case number and the case title. At this point, with the dropdown open, if you click the Add button, nothing happens! It ignores your input as if you hit the escape button, and the dialog disappears.
I did discover that hitting 'enter' will submit the textbox, and I've trained myself to do that instead of hitting the Add button. But it's still annoying. I have the same issue with the FogBugz search dialog.