Download the latest version of CUE and restart your computer. If that happens also try unplugging the peripherals and plugging them back in. That usually works for me.
I have the K95 Keyboard, Sabre RGB Mouse, MM800 Polaris Mousepad, and VOID wired headset, I use CUE more than most, ending the program via task manager and/or unplugging and replugging the peripherals almost always works for me.
The only problem I have ever had that I can't solve is Alt codes don't work, I think I have to program them in, and I'm really just too lazy to do it. The macros are legit though on the k95.