http://www.freerangemac.com/TransparentDock has a feature to lock the dock icons.
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A few new options were added!
* Fully adjustable transparency with 7 transparency levels
* Set the color & transparency of the dock background & borders
* Set the color of the triangles under open (running) applications (more colors)
* TD Themes palette allows saving & switching among custom dock themes
* Customize the dock poof effect
* Control the icon name font size
* Control the floating state of the dock
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Lock icons in the dock (disables icon dragging)* Allow Finder icon dragging
* Enable single application mode when switching applications from the dock
* Show or hide background-only applications
* Place Hide & Hide Others commands in the docked application popup menus
* Show or hide package contents in the docked directory popup menus
* Show or hide invisible & system files in the docked directory popup menus
* Control the depth of hierarchical menus from the docked directory popup menus
* & more...!
* All features can be selected & applied independently