I've had this issue since Mid May 2018 on my keyboard, RGB K70 (Brown). I was prompted by CUE 2.24.50 to update to iCUE 3.3.103. I went ahead and updated. Upon reboot, and once I was in windows, the K70 frantically started to connect and disconnect while iCUE was running in the background. The only way to stop the annoying sound was to quit iCUE. I tried all the polling rates and the problem persists.
Next, I rebooted again and this time around, my Windows boot got messed up. Again I tried all polling rates, but Windows refuses to load after the BIOS screen. The only way Windows loads is if I totally disconnect the K70 and plug it in once Windows loads to desktop. Tried booting with just the keyboard plugged in and all Polling rate, but still no luck.
Next, I uninstalled iCUE in safe mode, also cleared the %TEMP% folder. I booted to Windows (again with the keyboard unplugged) & rolled back to CUE 2.24.50 hoping that it would fix the issue, but it did not. The same issues persist, connecting/disconnecting keyboard. I even tried different USB ports where other peripherals work flawlessly. I even tried USB 3.0, but to no luck.
Next, from a previous corsair support ticket, I flashed the firmware that was provided by their team member, but the problem still persists.
And in this period of 7-8 days, the only thing I had installed and uninstalled was CUE/iCUE. No system drivers were updated, no GPU drivers were updated.
They keyboard is just under 3 years old. Everytime some problem crops up, it is due to a CUE update. Even back in Dec 2017, the malfunction lights issue got resolved after a CUE update. The Corsair forums are full of iCUE complaints. It seems to break the older hardware which Corsair might not have tested. Even as I type this, I have to use the K70 in BIOS mode, because the other polling rates disconnect my keyboard. I have never had to use the polling rates before. My system hardware too hasn't changed in 3 years.
Now when I click 'Check for updates' in CUE 2.24.50, it says that your software is up to date. Which only means that Corsair pulled down the upgrade for CUE 2.24.50 users. Only way to get iCUE was through their website. I really wish that Corsair could own up and acknowledge this issue.