Let me go ahead and say what I am using. I have the TiVo HD Series 3, Trendnet Wireless G router, the TiVo Wireless G adapter and a Windows 7 computer with the TiVo Desktop 2.8.3 version.
This is a solution I have found if your TiVo Desktop gives an error saying something like "no TiVo DVRs found" or "there was an error reaching your TiVo DVR". I also have some tips to suggest keeping your TiVo Desktop working.
If you get that error, whether or not your computer and/or TiVo is connected wirelessly, disconnect the router for 30 seconds and plug it back in. Start up TiVo Desktop and you should be able transfer now. If that still doesn't work, reboot your TiVo -- press the TiVo button on your remote, go to Messages & Settings, then Restart or Reset System, then Restart the TiVo HD DVR or whichever the top option says on yours, then press the Thumbs Down 3 times and Enter and let your TiVo reboot and try again.
I highly recommend when transferring recordings to a computer, have that computer connected to a WIRED connection through your router. Otherwise, DO NOT use any internet programs while transferring this will bog down everything and your transfers will timeout and most likely you will have to do the above again.
I had to do this before and it can be a pain but it helps to know what to do.
Note: If use any P2P or torrent programs that may cause these errors as I have stated.
On the good side, if you use a wired connection on your computer, you will be able to use the internet normally and won't have to worry about your transfers timing out.
I hope this helps those out there who have or have had this problem, this is the only way I have tried that works but don't know if there are any alternatives.
This may not work for everyone, we don't all have the same type of TiVo DVRs.