I'm seeing an odd problem with pppd on my 1.4.1 i386 system, and I'm
wondering if anyone else has ever seen this problem, or if it has been
fixed at some point.

After pppd has run for a while, it sometimes declares an LCP ECHO link
failure ("Serial link appears to be disconnected.") and hangs up and
redials (I have a 24x7 modem link).  About 30 seconds later, it
declares the link dead AGAIN ("Serial link appears to be
disconnected.") and hangs up and redials AGAIN, over and over again
until I kill the pppd daemon and re-start it.  I have the LCP echo
frequency set to 30 seconds with a failure count of 6 -- so 30 seconds
should not be enough time to discover a failed link.

So, is this a known problem that has been fixed for ages (and I just
need to get off my lazy duff and update my system), or is this a
mystery problem that plagues only my system?

(You know, it's amazing how well an IP link can actually work when
it's operational in only 15 second bursts every 30 seconds...)