I've actually had this problem numerous times with poser 6, even with the v3 injections loaded, I KNOW what you are talking about.

I can rotate dials to kingdom come for expressions, changes or muscles, even bigger chest......nada.

To fix this, click on ANOTHER body part, wait til you see it change to that body party (anything but what you really want to change) in the dial library (from "thigh" to say, "forearm", then go back and select the thigh, then try turning the dials again.

That usually fixes it for me.  no CLUE why it does that, drives me crazy.