I've been having this issue for a while now. I've tried TiVo Support twice now but their fixes have not worked and seem to be designed to maximize downtime to get me to give up in frustration. I have 4 TiVos on my network. 1 TiVo Premeire XL, 2 TiVo HDs, 1 Series 2. The Network is primarily a Home Plug AV Network (wired connection running over powerline) with a Linksys E3000 as the Home Router/GW, with one device (The Series 2) Connected over wireless. What happens is that periodically all of the TiVos will stop listing the other TiVos on the network and my PC's running TiVo Desktop. All other network functions work fine. I can connect to TiVo, browse and play YouTube videos, etc. i.e. I am 100% sure that I have network connectivity. If I tell any of the TiVos to reaquire and IP address (I'm set up using dynamic IPs allocated by the linksys), then it will see the other TiVos for a period of time. Sometimes minutes, sometimes hours. When I look on my Mac to see what is being advertised with Bonjour I see all of the TiVos listed. An interesting recent twist is that when I changed my PC to use the "old style" Tivo Beacon instead of Bonjour to advertise it stays up much more frequently on my TiVos than do the other TiVos or other PCs running Desktop using Bonjour. I also cannot find the TiVo Premiere via the IPad app. To answer some of the other obvious questions: 1. No I don't have a tuning adapter. All HD Tivos and the Premeire are running Multichannel Cable Cards. 2. Yes I really am sure I have IP connectivity, and that my home GW is not blocking ports. 3. Yes. Simply doing what is effectively an /ipconfig /renew (i.e. going into network setup and changing nothing but taking it all the way through the process) does restore the access to the other TiVos at least temporarily. 4. Rebooting the TiVo has the same effect. 5. I have tried rebooting the router also. 6. I have done the disable Home media at the Tivo Site, Reboot, Enable Home Media, Reboot. It had no effect.