NullPointerException in scanLegacyCustomDir when starting Hyperic 4.6.6 Agent on Linux

We are trying to start the Hyperic agent on Linux running as a standard (non root user) and the agent fails to start up with the following stack trace:

ERROR [AgentDaemonMain] [AgentDaemon@697] Error initializing plugins

java.lang.NullPointerException

        at org.hyperic.hq.agent.server.AgentDaemon.scanLegacyCustomDir(AgentDaemon.java:709)

        at org.hyperic.hq.agent.server.AgentDaemon.startPluginManagers(AgentDaemon.java:688)

        at org.hyperic.hq.agent.server.AgentDaemon.start(AgentDaemon.java:902)

        at org.hyperic.hq.agent.server.AgentDaemon$RunnableAgent.run(AgentDaemon.java:1015)

        at java.lang.Thread.run(Thread.java:662)

22-08-2012 17:10:46,696 EDT ERROR [AgentDaemonMain] [AgentDaemon@924] Unable to initialize plugin manager: null

org.hyperic.hq.agent.server.AgentStartException: Unable to initialize plugin manager: null

        at org.hyperic.hq.agent.server.AgentDaemon.startPluginManagers(AgentDaemon.java:698)

        at org.hyperic.hq.agent.server.AgentDaemon.start(AgentDaemon.java:902)

        at org.hyperic.hq.agent.server.AgentDaemon$RunnableAgent.run(AgentDaemon.java:1015)

        at java.lang.Thread.run(Thread.java:662)

I have enabled the finest level of logging, and disabled all plugins, and we still get this error. Any advice would be appreciated!