Several readers pointed out that you can delete the preferences file for Multi-resolutions (or any other Control Strip module) without having to delete the entire Control Strip preferences file (as suggested last time).
The trick is to use ResEdit. Open the Control Strip Preferences file. Then open the "pref" resource. Here you will see a list of the preferences for each module that has any preferences. You can then cut the preferences just for the module you wish.
Also, Cristian Viola notes that if your screen goes black after selecting a resolution - so you cannot see the dialog box that asks whether you want to revert back to the prior resolution - hit the Escape key. This should get you back to where you once belonged.