Answering my own question here thanks to an old thread on a similar issue.

Seems that I encountered a bug/issue whereby despite stream authentication being disabled in OpenWebIF, that it was enabled in the "Customize" menu.
I ho[e this is of some use to anyone encountering similar issue


Quote Originally Posted by pembo View Post
you've probably got authentication for http streams turned on... it's within the customize menu. you can set this in openwebif also...