Henry, this is failing because the storage group you are using is already in a view.  You can simply create a new storage group with a different name and add the same devices from the existing storage group to a new view.  You can use cascaded storage groups if you wish but you can't have a storage group in multiple views. 
We have a backup data mover server that needs to have visibility into multiple VMWare cluster storage groups on a VMAX-1.  The current plan is for the backup server to view 3 separate clusters as well as it's own SG with boot LUN, etc.  This can be accomplished with cascaded initiator groups, although I ran into a PowerPath issue when the backup server had more than 16 FA ports zoned to 2 HBAs.  Also, we have to avoid using the same FA port between the clusters as well as the backup server, so it may become an issue with future expansion.  I tried using cascaded storage groups, but when I try to add the cluster's SG into the backup servers parent SG, it gives and error 'Cannot perform the requested operation because the group is currently within device masking view'.  Is it possible to create cascaded storage groups in this scenario?  The clusters all have their own SG and the backup server has it's own as well.  Has anyone else been in this scenario and what solution did you use?  
Backup server - view LUNs from VMWare clusters