Well having just brought a K55 RGB and straight away am having the caps lock and num lock light problems I am totally stunned a brand like Corsair cannot solve this problem.
I can reproduce this problem 100%, plug then unplug any USB device, or indeed an SDHC card(uses the USB bus) and the caps lock and num lock light stop functioning, unplug and re-plug KB and works again!!
Over 2 years and this is still a fault. I am really upset that I have spent money on several Corsair products over the years, not anymore!