Believe process 2012 did not start until CS6 or ACR 7.x.
The 6.7 camera raw version for cs5 has process 2012, but there are some limitations with using it in cs5.
Is your camera raw updated to version 6.7
(camera raw 6.7 is the newest version that works in cs5)
Yes, I have updated to 6.7. There was a brief period after upgrading from CS4 to CS5 that the 2012 process worked. I'm not sure when I lost the ability to use it.
As far as i know process 2012 was only in camera raw 6.7 to make cs5 compatible with images sent from lightroom 4 to photoshop cs5, but you can't adjust
any of the process 2012 adjustments in camera raw 6.7.
Of course photoshop cs6/cc is fully process 2012 enabled, so one can do all the adjustments that are missing in camera raw 6.7
(camera raw 7.x and 8.x)