I faced a similar problem an Indigo, this was my error log
javax.naming.CommunicationException: Could not obtain connection to any of these urls: localhost:1099 and discovery failed with error: java.lang.ClassCastException: java.lang.Boolean cannot be cast to java.lang.String [Root exception is javax.naming.CommunicationException: Failed to connect to server localhost:1099 [Root exception is javax.naming.ServiceUnavailableException: Failed to connect to server localhost:1099 [Root exception is java.net.ConnectException: Connection refused]]]
I tried the nightly build an indigo and now it seems it detects a running instance even when no other server is running. If I decide to launch it anyway everything works fine though.