Yeah, there's a bug of some sort in the click handling. I haven't been able to narrow it down, though I'll admit I haven't tried particularly hard because pretty much everywhere I use it are keyboard-centric UIs (so up/down arrows, esc, enter instead of a mouse). These days, most of the places I need autocomplete I now use a hacked up version of the jQuery UI control, so I'm probably not going to being investing any significant effort into the ComboBox unless it becomes an issue with one of those apps that already use it.

The event handling stuff is pretty simple; that's where the problem is, not in the internal functionality that actually does dropdown/input stuff. My gut tells me that it probably has something to do with child elements within the dropdown items and the event bubbling stuff that JavaScript does, but it's been years since I've looked at it.

The API is well organized and documented. The site provides numerous examples and an active forum. I'm not necessarily a true believer; but, what's there I have found more accessible than any other OSS solution I've come across.