Comment 1 for bug 498245

The specific problem you're having (from reading the other referenced bug report) is that adding the delay causes the bridge to take longer before it's brought up, and upstart doesn't wait for the bridge to finish being brought up before running the init scripts in /etc/rc2.d. However, upstart doesn't wait for *any* interfaces to be brought up before processing /etc/rc2.d, bridges or otherwise; there's a general race condition here that happens to be fixed for you when speeding up the bridge init, but solving the race generally needs to be done in the munin package:

 - the munin package needs to provide an upstart job in place of the init script
 - you will need to modify the upstart job to specifically wait for the bridge interface to be up ("start on net-device-up IFACE=br1") to match your specific needs of binding to a particular interface.