OpenLayers addControl OverviewMap 'a is null' OpenLayers.js (line 1244)

Question

I am trying to add an OverviewMap to an open layers map. I am receiving the following error in firebug:

a is null [Break On This Error]

...ntUpToTier:null,tierSizeInTiles:null,tierImageSize:null,initialize:function(a,b,...

OpenLayers.js (line 1244)

I receive this error when adding control to map object like this:

http://trac.osgeo.org/openlayers/wiki/Control/OverviewMap

but also I receive the same error when I pass a new OverviewMap object when instantiating a map like in the following tutorial: http://openlayers.org/dev/examples/controls.html

I have made sure to pass my non-default options to the new OverviewMap

Has anyone run into this before? I am using zoomify tiles would that be an issue with creating an overview map?? Thank you.