EFI and SUN Disk Labels
There is a good document on docs.sun.com which shows some of the differences between the two formats but suffice to say that you cant install Solaris on an EFI disk. In a nutshell, you need to change it to an SMI label.
Easily done by simply using 'format -e’. select the label option, and then SMI label.
Once you have done that you can check the partition table as normal and restart the install successfully