shared_transport concurrency failure - starting NotificationBusses at the same time causes "timer cannot be retrieved from protocol stack"

I have an application that starts four jgroups NotificationBus's that all share the same UDP transport (with singleton_name="...") but are otherwise distinct. Recently, the application started to fail to start with the following stack signature:

2009-04-27 13:56:50,425 -0500 ERROR [JGroupsTest] - Exception running bus
org.jgroups.ChannelException: unable to setup the protocol stack: timer cannot be retrieved from protocol stack
at org.jgroups.JChannel.init(JChannel.java:1574)
at org.jgroups.JChannel.<init>(JChannel.java:257)
at org.jgroups.JChannel.<init>(JChannel.java:240)
at org.jgroups.blocks.NotificationBus.<init>(NotificationBus.java:69)
at JGroupsTest$1.run(JGroupsTest.java:25)
at java.lang.Thread.run(Unknown Source)
Caused by: java.lang.Exception: timer cannot be retrieved from protocol stack
at org.jgroups.protocols.Discovery.init(Discovery.java:98)
at org.jgroups.protocols.PING.init(PING.java:84)
at org.jgroups.stack.ProtocolStack.initProtocolStack(ProtocolStack.java:641)
at org.jgroups.stack.ProtocolStack.setup(ProtocolStack.java:468)
at org.jgroups.JChannel.init(JChannel.java:1570)
... 5 more

I created a test application that does nothing but start these four busses, and if I start them simultaneously, I can always reproduce the above error. I will attach the test application.