ListBox绑定在测试配置中不起作用

I'm having trouble with binding a ListBox and I can't for the life of me figure out what's wrong. Most of the time it works fine, but in a special test configuration I have for my application it doesn't work and it's driving me crazy. I've literally stared at it for hours and tried all sorts of things. It's gotta be a binding issue, but I can't find it. There aren't any exceptions or binding errors being thrown that I can see.I'm having trouble with binding a ListBox and I