It appears that the recent changes to libpcap and bpf_filter stuff have 
broken pppd.  In particular, pppd no longer seems to be able to parse an 
`active-filter' expression of the form:

	active-filter "udp or (tcp and not tcp port ntp)"

I've had to remove the above line from my /etc/ppp/options file in order 
to get pppd to come up.  With the above line left in, pppd never even 
gets to forking itself into the background.