That issue has been reported before, and it only happens with the latest Yocto image version. Hopefully it will be fixed in future releases, but in the meantime I recommend you to re-flash the Edison with the following image version: Intel Edison Software Release 2.1
You can flash the Edison using the Flash Tool Lite. You can download it from the following site: IoT - Intel® Edison Board Download | Intel® Developer Zone
Thank you Diego, you saved the day. I did what you said, it works perfectly.