Since firmware 3.0, there is a software lock function in the menu that allows you to choose almost all of the functions, buttons, settings of the camera. You can select the button, dials that you want to lock to prevent accidental changes.
After selecting which functions or dials to lock in the menu, you have to enable the lock function itself. In the lock menu, you have the options of locking all, unlocking all, or lock the user-specified options. Hope it helps, Currently, i lock veirtually everything except the iso, shutter speed.