Datastax Enterprise is crashing with Unable to gos

I am trying to stand up Datastax Enterprise Cassandra cluster in AWS. I am not able to bring up the first node (seed node) due to error: Unable to gossip with any seeds. I must say that the first time I installed Datastax Enterprise, it worked for me; However, I wanted to make it a multi node cluster and made changes to the "seeds" parameter to the private IP instead of the default "127.0.0.1"

Here are the details: Datastax Enterprise 4.x installed on Centos 6.4, in a single node set up. Following are the values I changed in the default cassandra.yaml: cluster_name: 'xxxCluster' num_tokens: 256 listen_address: 172.x.x.x rpc_address: 172.x.x.x - seeds: "127.0.0.1" endpoint_snitch: com.datastax.bdp.snitch.DseDelegateSnitch

java.lang.RuntimeException: Unable to gossip with any seeds
    at org.apache.cassandra.gms.Gossiper.doShadowRound(Gossiper.java:1191)
    at org.apache.cassandra.service.StorageService.checkForEndpointCollision(StorageService.java:443)
    at org.apache.cassandra.service.StorageService.joinTokenRing(StorageService.java:642)
    at org.apache.cassandra.service.StorageService.initServer(StorageService.java:610)
    at org.apache.cassandra.service.StorageService.initServer(StorageService.java:501)
    at org.apache.cassandra.service.CassandraDaemon.setup(CassandraDaemon.java:362)
    at com.datastax.bdp.server.DseDaemon.setup(DseDaemon.java:376)
    at org.apache.cassandra.service.CassandraDaemon.activate(CassandraDaemon.java:480)
    at com.datastax.bdp.server.DseDaemon.main(DseDaemon.java:639)
ERROR [StorageServiceShutdownHook] 2014-05-01 22:26:00,378 CassandraDaemon.java (line 198) Exception in thread Thread[StorageServiceShutdownHook,5,main]
java.lang.NullPointerException
    at org.apache.cassandra.gms.Gossiper.stop(Gossiper.java:1268)
    at org.apache.cassandra.service.StorageService$1.runMayThrow(StorageService.java:569)
    at org.apache.cassandra.utils.WrappedRunnable.run(WrappedRunnable.java:28)
    at java.lang.Thread.run(Thread.java:722)

I have tried clearing the /var/lib/cassandra directory, changed the "seeds" back to the default "127.0.0.1", but I still keep getting the same error. In fact I even removed the Datastax Enterprise package using "yum remove dse-full", re-installed Datastax Enterprise again, but still keep getting the same error.

I would appreciate any help I can get.