I have run into a bit of a problem this morning...
My windows update popped up an update for my silicon labs CP210x USB to UART bridge which I let it install without thinking about it.
This obviously replaced the drivers but when I run Zadig and replace them again, cgminer does not see the miners.
Any suggestions?
Manually uninstall any installed drivers via device manager, unplug, restart, replug (different USB port if you can), start again.