Reset to Defaults - Not Working

The reset to defaults button has no effect after:
1) Changing settings to use lightbox lite and saving configuration
2) Later modifying settings to not use lightbox light and attempting to save configuration results in a number of fields which are now empty. Trying to reset to default values by selecting the defaults button only results in the same error messages.

I found this out after noticing a bug report using firefox and firebug (it reported that the lightbox_lite setting were undefined)