iMac won't restart with USB hub plugged in
I have a 2013 iMac running 10.4.1. I've had an Anker powered USB hub in for years. Noticed recently that the iMac will hang on a black screen on restarts until i unplug the hub.
I tried a pram reset and basic maintenance in Cocktail.
Could the hub be defective now? if so, any recommendations for a new one?
You need to do some troubleshooting before assuming it's the USB hub. It could be the hub but it also could be a cable or one of the devices connected to the current USB hub. Remove all devices from the Hub and startup with the hub only, if it successfully boots then it's likely one of your devices. You will need to add each one by one until the problem comes back.