I recently started working for a client that uses OpenVPN. I have really only had experience with Cisco VPNs up to this point (and the VPNC client). While troubleshooting my new connection, I noticed that every time I either connected to or disconnected from a VPN using NetworkManager, it produced this error in my daemon.log:

nm-dispatcher.action: Script '/etc/NetworkManager/dispatcher.d/01ifupdown' exited with error status 1.

After searching a bit on Google, I found this bug that said the actions passed to the 01ifupdown script by NetworkManager were vpn-up and vpn-down. Since those actions were not handled explicitly in the script, they were throwing an exception as designed. NetworkManager should not be calling the script with an undefined action. There was a trivial patch attached, which basically addressed the two missing actions by adding vpn-up to the up case and vpn-down to the down case.

--- 01ifupdown	2010-01-04 11:51:45.732239244 +0000
+++ 01ifupdown.new	2010-01-04 11:51:27.080203723 +0000
@@ -17,7 +17,7 @@

 # Run the right scripts
 case "$2" in
-    up)
+    up|vpn-up)
 	export MODE="start"
 	export PHASE="up"

@@ -32,7 +32,7 @@

 	exec run-parts /etc/network/if-up.d
 	;;
-    down)
+    down|vpn-down)
 	export MODE="stop"
 	export PHASE="down"

Success! No action and no more error messages either. It appears that this is fixed in future versions of NetworkManager (i.e. Natty Narwhal) but not yet in Lucid Lynx or Maverick Meerkat.