Not super familiar with Solaris 11 or x86, but that error usually means driver problems or physical device path changes (possible with BIOS upgrade. If you can try this:
mount into single user regulary, off the net or from cdrom:
boot net -s
boot cdrom -s
then mount your primary hard drive on /tmp/a (or somewhere similar)
moutn /dev/dsk/cxtxdxsx /tmp/a
then cd into /tmp/a/etc and backup your path_to_inst file
cp path_to_inst path_to_inst.bak
then get back to your ok> prompt (or x86's equivalent) and run
(-a will ask you questions and -r will attempt to recontruct your physical device paths and the logical device paths)
answer defaults to all questions and, when it notices that your path_to_inst is missing and would you like to recreate it, answer yes.
Then try your regular boot.
At the boot prompt, you can also try to do:
a good trick, if you're not sure what options you have available at the lower level is to use the sifting command:
will list all the commands available at the prom level with the word probe in them
Hope this helps, or, at least, gets you pointed in the right direction