I've had this problem before in Poser 6. By trying to repeat the problem I've found the following two reasons for parameter "lock"

Sometimes my morphs revert to zero immediately after I save a file and the "save as..." dialogue box disappears. Pose and Camera and Lights are not affected, only the morph dials on the body and head of my figure. This doesn't happen often and I'm not sure why this occurs but I found that I can just close the current file and then open the version I just saved and everything is fine (the correct morphs were saved).

Secondly, I've had parameters lock after adding and deleting a lot of other figures in the scene. Say for example I bring up a figure and add morphs and then add a character set... then add and delete a bunch of clothes and hair figures and props (tests for myself or the client)... When I go back to make edits to the figure body and head dials, they are all stuck with the current morphs and don't change. I can change rotations and bends for body parts, but body part morph dials no longer work. The only way I've been able to get over this is to go back to a previous save and redo the lost work.

I just got Poser 7, so maybe these bugs will be fixed.