Device status down

Hi,

I have installed and run Zenoss a couple of time now, but never on Centos, always on Ubuntu and by no means a Zenoss Guru. I have just gone through an install of Zenoss. After a couple of problems relating to dependencies and zenjobs not starting due to permissions on the /dev/shm directory. I thought everything was smooth after this, but once I did a device into the system, the device status goes to down. Once I delete the event, the Device immediately turns to up but then after 30 seconds it goes down again and the devices just stay down. I have added 3 devices and all the same. The Zenoss system can ping the devices manually via the Zenoss UI and CLI. I am a little lost.

Running Zenoss 4.2.5 on Centos 6.

Any ideas

Thanks
Ross