I was having exactly the same problem: The only way to setup a wifi connection was to have an active ethernet connection while setting up wifi. Then the wifi would remain active (at least for a while) after the ethernet cable was unplugged. This was happening with an Asus RT-N56U router. The issue was not 2.4 GHz vs. 5 GHz as someone else was experiencing, because I had the router configured with different SSIDs for each and tried both with the same results. I had no trouble with nearly a dozen other networked devices in the house. Recently my router started to fail and I replaced it with a Netgear R7000. The TiVo (and every other device) connected on the first attempt at and has remained stable since. I've tried 2.4 GHz and 5 GHz. I've rebooted both the router and the TiVo multiple times, and I've configured and reconfigured wifi on the TiVo at least 5 times. The TiVo connect immediately every time and stays connected. FYI, I'm using the same SSIDs and WPA2 passwords as on the old router. I didn't have MAC address filtering, firewalled ports or anything even a little exotic on either router. It seems as if there was some incompatibility or out of the box configuration mismatch between the Asus and TiVo that I never figured out. I would have been interested in exploring the issue a little more now that I have a TiVo setup that I know works. However, the Asus is toast, so I guess my particular case is going to remain a mystery to me.