This occurred when I was trying to add a HP MSA1500 SAN which consisted of just 1 LUN as a datastore. I managed to get through the screens but no further than the formatting section.
To resolve this someone on the VMware forums mentioned about deleting the array containing the logical drive on the SAN and recreating a new but different RAID array before deleting again and recreating Array and Logical drive to meet your original requirements.
1. Attached a Windows server to the SAN via FC HBA
2. Opened the HP Array Configuration Utility and deleted the Array containing the RAID 6 logical drive
3. Created a new array with a RAID 0 logical drive
4. Deleted the array
5. Created a new array with a RAID 6 ADG logical drive
6. Went back into the vSphere client, rescanned the HBA and was able to add the logical drive without error