Newly created Themes don't appear in Theme Chooser

I've recently made two new themes for Keynote, but they don't appear in the chooser both when creating a new Keynote presentation or to apply to existing keynote presentations...

No idea what to do or why.

-- The theme files are easily visible under ~/Library/Application Support/iWorks/Keynote/Themes

-- On 'Show Package Contents' the only clearly different thing is that the new themes have no "themeMetaData' -- but copying between packages makes no difference..

Any help on this would be MUCH appreciated -- even suggestions.

Is there any way to rebuild Keynote's recognition of the ~/Library/Application Support/iWorks/Keynote/Themes folder, for example?

This problem has appeared since Lion install.

UPDATE:

I've discovered that if I change the file extension on the theme file from .kth to .keynote, it appears in the Chooser and can be applied -- but in the Chooser the file is a blank icon.... 😟