Have you tried going back into "Control Panel" then "Sound" and setting as not default and then resetting them as default? Sometimes programs can mess with the settings, as well as other things.
If this doesn't work, try uninstalling the driver(s), reboot and then reinstall them. Then try setting them as default again.
When in the "Sound" area of "Control Panel" you may also want to try clicking the "Configure" button.
If none of this works, try a different headset. I know you said they work on another device, but devices are picky. If the other headset still won't work, then you may well have to look into if the jack is loose or needing replacement.
Before opening up the device and doing anything, I would first check to see if it is still under warranty. If it is, then contact the manufacturer about a repair/replacement.