Very often, the first time I try to connect to my ISP (using RP3), PPP will make a connection and log on but immediately get a SIGHUP after the Connect: ppp0 <--> /dev/ttyS2 line. This doesn't happen with KPPP or with a manually created ppp-on script. It did, however, also happen with the original RH 5.x netcfg script, presumably with the netcfg script in 6.1 as well.
This is fixed in the errata pppd release.