There is a problem when your pptp connection goes down and up. Openswan needs to re-bind the ipsec0 interfaces to the new ppp0 interrface.
This is best done by adding the fiollowintg 4 lines to /etc/ppp/ip-up:

if [ -f /var/run/pluto/pluto.pid ]                                             
then                                                                           
        ipsec tncfg --detach --virtual ipsec0 > /dev/null 2> /dev/null         
        ipsec tncfg --attach --virtual ipsec0 --physical ppp0                   
fi       

without openswan running the pid file would not exist, so this should not affect anyone else.

Paul

You shouldn't change /etc/ppp/ip-up for that. That's what we use hotplug for.
With hotplug scripts you also don't have to care about whether the interface you're attaching to is ppp, vlan or whatever...