while using rp3 graphical ppp interface controller.
(and hence ifup/ifdown)
scenario:
left click on rp3, window pops ups, bring up interface ppp0? yes or no
click yes
blah, blah, blah it dials and connects, ppp0 is brought up.

if the interface is brought down unnaturally(the other end disconnects,
phone line is unplugged...) and the interface is configured to reconnect,
then it will enter a loop trying to reconnect.

now the problem:

if, while in this loop, you click on rp3, it will pop open a window asking
you whether you want to bring up interface ppp0. if you click yes, then i
deduce that a new ppp-watch is spawned which creates the file
/var/run/pppwatch-ppp0.pid with its own pid and tries to bring up the
interface, which fails since the modem is locked, it then exits removing
/var/run/pppwatch-ppp0.pid.

the old ppp-watch is still in its loop trying to bring up ppp0, but any
attempt to bring the interface up or down will fail since the file
/var/run/pppwatch-ppp0.pid is gone.

ppp-watch should check to see if /var/run/pppwatch-ppp0.pid exists
and then if the pid is valid, or whatever action you decide is right,
you're the experts. :)

-brandon