Kween, you said "nothing has changed in my phone service. (Time Warner, SoCal)". You may not have changed anything, but there's no way to know that Time Warner hasn't. That pretty much goes for everyone (no idea if your local or long distance providers changed anything).
I think it's a safe bet if you have POTS (plain old telephone service) from a traditional phone company you're still being served by a digital switch (5ESS, DMS100, etc) and your "local loop" probably hasn't changed. Your calls are encoded to a full 64kbs no compression and switched using very low latency circuit switching techniques. Modems/faxes work great with this setup on local calls.
For everyone else, (VoIP, Cable phone, etc) all bets are off. They probably use packet switching and probably even compress the data to make things more efficient. Yes, you can get more calls down a wire, but the latency increases and that and compression makes modem use very difficult. If it worked yesterday, it may not today because the call could be routed differently or equipment somewhere is "upgraded" to be more efficient.
Now let's add long distance into the mix. While a traditional phone company may not have replaced it's switches, the long-distance market is very competitive and more modern. They are much more likely to use packet switching and even VoIP making modem calls less reliable.
For the LaHo dialup modem, I have a single POTS line with a high quality modem right next to me (US Robotics V.Everything). I know I'm connected to a 5ESS switch less than a mile away. Very often I hear folks try and call and are unable to connect. Their modem tones sound great on the speaker, but the modems just don't sync up. It hurts to hear them keep trying
I think those folks who can't connect to me, can't connect to ReplayTV (well, Earthlink, or whoever) for the same reason. The technology has changed and they no longer have full bandwidth low latency connections. There's nothing we can do about it. Like analog TV, I'm thinking a modem's time is almost up.
If you want to keep using a ReplayTV reliably, you should upgrade to an Ethernet connected unit. (4k or 5k). They're cheap and should keep working no matter what happens to the ReplayTV service or dialup.
For now, if you want you can try calling the LaHo test line. (search the forum for LaHo Goodwill, or read at Percdata.com for instructions ) If you want me to listen in on this end we can set up a time convenient to both of us.
Note 1: I work in voice telecom on systems doing routing and billing. I'm somewhat familiar with how these systems and industry work, but am certainly not an expert, nor do I know how your particular system is set up. I've been playing with modems since the early 80's. (Novation Cat acoustic! @300bps)
Note 2: I'm not sure how long I'll be keeping the LaHo modem line around. It's costing $36/mo and there are no paying customers using it. One person uses it to set their clock daily, so I know it's working
. It's been a while since it passed guide data to anyone. LaHo isn't going away, but the modem line might.