It turns out that fixing this correctly involves very invasive, far-reaching changes to the way that Lightroom handles menus on Windows. These changes were too extensive and potentially destabilizing to be thoroughly tested in time for the 5.5 release. So, we have opted for a temporary fix that is incomplete, but much safer than the real fix. As such, it is still possible to hit this bug, but it is much less likely. And if you do hit it, the consequences are much less bad. We plan to provide a real, complete fix in a future update.