Steps to reproduce (on Chrome 33/Ubuntu 13 with Unity):
- open lightbox
- press and hold Alt
- press Esc
- release Alt
Task selection OS interface appears when pressing Alt+Tab, disappears when pressing Esc (which is the normal way of exiting the task selection interface without actually selecting a different task). Lightbox is undisturbed.
Task selection interface works as expected, but the lightbox is also closed.