Comment 3 for bug 1501004

I also investigated the "focus" theory a bit further:

// Find evolution window id
$ xdotool getmouselocation

// Focus the "TO" input field, type some letters follow by [AltGr] + [2] (@ on Danish keyboard)

$ xev -id 23181333 -event keyboard -event focus

KeymapNotify event, serial 17, synthetic NO, window 0x0,
    keys: 4294967236 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
           0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

FocusIn event, serial 18, synthetic NO, window 0x161b815,
    mode NotifyNormal, detail NotifyNonlinear

KeymapNotify event, serial 18, synthetic NO, window 0x0,
    keys: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
           0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

KeymapNotify event, serial 18, synthetic NO, window 0x0,
    keys: 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0
           0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

// This seems to be the problem
FocusOut event, serial 18, synthetic NO, window 0x161b815,
    mode NotifyNormal, detail NotifyInferior

FocusOut event, serial 18, synthetic NO, window 0x161b815,
    mode NotifyGrab, detail NotifyVirtual

FocusIn event, serial 18, synthetic NO, window 0x161b815,
    mode NotifyUngrab, detail NotifyVirtual

KeymapNotify event, serial 18, synthetic NO, window 0x0,
    keys: 0 0 0 0 0 0 0 0 0 0 0 0 0 16 0 0
           0 0 0 0 0 0 0 0 0 0 0 0 0 0 0 0

So to me this seems to confirm the theory.
Any XOrg gurus out there who can confirm this and can figure out who steels the focus? Invisible Ubuntu HUD?