We discussed the same issue on this thread recently:
http://forum.corsair.com/v3/showthread.php?t=175837
As far as we're concerned, this seems as a CUE related issue - as killing the process and restarting it restores normal and expected behaviour (and of course using the volume slider instantly locks those keys out of use).
As I am doing so now, I strongly encourage anyone facing this exact same issue to let Corsair know of this by submitting a ticket on support.corsair.com (or using the support ticket system at the top of this page).
