Came across this myself the other day. The issue is that on boot both /etc/init.d/startvpn and /etc/init.d/initswitch are enabled and run at boot time.
I wanted the to use the switch to control vpn so I just disabled the startvpn script:
/etc/init.d/startvpn disable
Hint: you can tell what is enabled by looking at contents of /etc/rc.d