Transport Error - HTTP Code: 0

Tried to execute following with 'Hands on demo'

isc.HTMLFlow.create({
ID: "html",
width:800, height: 600,
evalScriptBlocks: true, contentsType: "page"
})

html.setContents("<script src='URL' TYPE='text/javascript'></script>");

where URL is a valid link to existing .js file and got back
Transport Error - HTTP Code: 0

However when I use html that contains that script and use following

html.setContentsURL("URL");

HTMLFlow is diplaying proper content.

Am I missing something?