hebus on "dse dead but pid file exists"

I've just installed DSE 3.0 with opcenter.
When I launch it with sudo /etc/init.d/dse start it seems to work :

it returns:
Starting DSE daemon dse
DSE daemon starting with Hadoop and Solr disabled (edit /etc/default/dse to enable)

But if I try to connect to the tutorial "Test Cluster" (so localhost) with opcenter (on a distant machine but with port 8888 shared) I got this error:

Error creating cluster: Unable to connect to cluster

And if I check the health of dse with sudo /etc/init.d/dse status: I got:
dse dead but pid file exists

Any idea of what is happening? or log file to look?