I have a Corsair K95 mechanical keyboard and I do use its programmable hotkey capability, but nothing with 'CTRL-L'. I also use other programs like SnagIt with associated hotkeys. I've had the keyboard for about 6 months now and I'm pretty sure the problem didn't exist for that long... maybe 4-6 weeks? The keyboard seems to work fine as far as I can tell. Previously, I used a Logitech programmable keyboard and never had this issue.
On a wild (lucky) guess, which seems to be working so far, I changed 'Media Key Mode' in MC (Options-General-Advanced) to 'disabled' from 'automatic' and the problem immediately disappeared. I don't really use that MC functionality anyway right now so not a big deal, but it's pretty weird that it would start happening seemingly out of the blue.
Jim, I'm running the latest build on Windows 10 Ultimate x64 and using its built-in antivirus capability (don't know if I can turn that off). I run an optical cable from the PC to my Yamaha RX-A820 and play... well... music.