ERROR :  

[root@RAC01 cssd]# /oragrid/product/11.2/bin/crsctl check crs
CRS-4638: Oracle High Availability Services is online
CRS-4535: Cannot communicate with Cluster Ready Services
CRS-4530: Communications failure contacting Cluster Synchronization Services daemon
CRS-4534: Cannot communicate with Event Manager

When Trying To start Oracle Cluster with following Command :

[root@RAC01 cssd]# /oragrid/product/11.2/bin/crsctl start crs
CRS-4640: Oracle High Availability Services is already active
CRS-4000: Command Start failed, or completed with errors. 

When Trying To Stop Oracle Cluster With Following Command : 

crsctl stop crs command failed

[root@RAC01 cssd]# /oragrid/product/11.2/bin/crsctl stop crs
CRS-2796: The command may not proceed when Cluster Ready Services is not running
CRS-4687: Shutdown command has completed with errors.
CRS-4000: Command Stop failed, or completed with errors.

Solution is Simple :

Just Run 

[root@RAC01 cssd]# /oragrid/product/11.2/bin/crsctl start cluster 

[root@RAC01 ~]# /oragrid/product/11.2/bin/crsctl check crs
CRS-4638: Oracle High Availability Services is online
CRS-4537: Cluster Ready Services is online
CRS-4529: Cluster Synchronization Services is online
CRS-4533: Event Manager is online

Thank you
Osama mustafa