I know! That's what struck me as odd (apart from my modem suddenly working again)! I can't explain it.
But I know my modem wasn't working because I'd get the messages on my Tivo telling me how my unit has failed to make the daily call. And I quickly discovered that it wasn't getting a dial tone (and all my attempts at fixing it and changing the settings did nothing).
I was able to force a call by picking up my phone and hanging up once the Tivo connected (when I picked up an extension phone, I got a dial tone, and the Tivo would then call out). I forced a call using that method a handfull of times (like once a month or so) and then just stopped.
Come to think of it, I think the last time I forced a call was earlier this year - back in the Spring. I remember my Tivo was acting weird after the call, and I think that might have been the reason I stopped forcing the calls. I can't remember what the "acting weird" consisted of, but it was something I didn't like (like maybe deleting my ToDo list or something). Is it possible I got 6.3 way back in Spring, when I forced that call?
In any case, this 6.3 update seems to have fixed my Tivo's ability to phone home again.