Ok the problem was effectively a memory problem (I used eucalyptus to run instance on my cloud and change type from small to m1.xlarge solved the jmx connection problem).
So now, DSE doesn't stop after I run opscenterd-agent.
But, It still doesn't work...
First I've got a redudant: INFO [Initialization] 2013-08-27 10:35:01,042 Sleeping for XXs before trying to determine IP over JMX again
So I've edit my adresss.yaml file and add: local_interface: "127.0.0.1"
=> redudant and blocking JMX INFO is gone!
But I run into an other error:
Error getting devices and partitions
java.io.IOException: Cannot run program "iostat": error=2, No such file or directory
my full log here: http://pastebin.com/8mzHqsvZ