This worked for me:
1. Do NOT plug in USB.
2. Install Line 6 Monkey, keep USB unplugged, do NOT install drivers or anything, reboot.
3. Install POD HD500X Edit, reboot.
4. Make sure Line 6 programs are closed.
5. Open Line 6 Monkey, and install drivers (see above "Allow" comment, if applicable), reboot.
6. Plug in USB.
7. Open Line 6 Monkey to ensure USB is recognized.
8. Open POD HD500X & begin receiving presets.