Thread:Extension talk:Widgets/Smarty can't find its libs -- breaks Widgets extension

Facts:
 * mediawiki 1.20
 * PHP 5.3
 * extension Widgets installed in extension/manual/Widgets. This is loading OK
 * Widget:Iframe, Widget:Flickr installed
 * setup test page for each, got the same error: "Error in widget Iframe"  or "Error in widget Flickr"
 * Wiki Debug Log shows:

... Article::view: doing uncached parse Class Smarty_Security not found; skipped loading Class Smarty_Internal_Resource_Registered not found; skipped loading Title::getRestrictionTypes: applicable restrictions to Widget:Iframe are {edit,move} Class Smarty_Internal_TemplateCompilerBase not found; skipped loading Title::getRestrictionTypes: applicable restrictions to Widget:Iframe are {edit,move} Class Smarty_Internal_Templatelexer not found; skipped loading Class Smarty_Internal_Templateparser not found; skipped loading Class Smarty_Internal_CompileBase not found; skipped loading Title::getRestrictionTypes: applicable restrictions to Iframe test are {edit,move} ...

I poked around in Widgets/smarty/libs/sysplugins and I can see the needed files.

I'm stuck. Any ideas?