SEVERE:Number of new nodes being added are not equal to number of new virtual nodes. Silent install cannot continue.

If you are using Grid Naming Service (GNS) and got this error, try to use sintax for not GNS:

"CLUSTER_NEW_VIRTUAL_HOSTNAMES={oralab4-vip}" 

details: http://martincarstenbach.wordpress.com/2009/10/12/build-your-own-rac-system-part-iv-extending-grid-infrastructure/