Yes, there have many posts over the past few months about modem issues.
Earthlink ( the primary dialup ISP) was cleaning up their network and it was causing lots of problems. There was also ReplayTV dialup authentication problems. We (user community) don't know exactly what the causes are but I think they will continue. Once you get a working phone # keep using it and hope for the best.
If you use a VoIP phone service or a LD VoIP service, that *really* makes things tough (Cable Co phone is VoIP too). The modem protocols were simply not designed for it and don't do well over them. Some VoIP services have implemented special hacks for FAX, but I've never heard of one doing it for data protocols. It's really hit and miss and may vary with your and your ISP's network load, time of day, phase of the moon, local sport team record, what you had for dinner, etc.
BTW, I wasn't concerned about PERC... I know when folks have problems (I hear the modem answer and try to sync). When someone is trying to get it to work, it rings a lot
If someone wanted to do a Replay modem test, calling PERC isn't a bad idea, I know it works (most of the time)