This one is a killer. :)
After some time running on a leased line, the modem (USR Courier) goes
down. This would be no further problem, as it (re)starts from inittab, but
since installing RH6.1 (kernel 2.2.14, ppp 2.3.11), sometimes pppd does
not notice that the line is down. Furthermore, when killed, it does not
get restarted by init. When restarted (manually or by editing inittab and
HUPping init), it logs "pppd started by root", then hangs (it should start
/usr/sbin/chat to get a connection). No exit, no messages/logs. Strange
thing, when started through strace or ltrace, everything performs ok.
Of course, a reboot fixes things.
I'm not sure if this is a ppp-only problem. There might be something else
broken in the system...
Please verify this with a newer version of Red Hat Enterprise Linux or Fedora
Core and reopen it against the new version if it still occurs.
Closing as "not a bug" for now.