Divices not showing in Infrastructure>Devices !!

Hello to all zenoss users and masters,

I'v recently encountered a problem in Zenoss 4.2.5. The problem is that devices in Infastructure>Devices tab are not showing anymore. I can actually see the events are showing from those devices and able to proceed to device options from Events tab. What have been done:
1. Tried 'Production state' visibility options, checked all the boxes and nothing changed.
2. Tried to add devices again - error - device already exists
3. Tried to delete and add device again - no luck.
4. Restarted server/service - nothing.

Desperately need help. Appreciate your help.