Your comments

Note: Replaced angled brackets with square ones so the HTML code shows up in the forum post.
One thing of note... the line

[script type="text/javascript" src="]

appears in the header of the page, but the element that is meant to play the TTS animation is loaded via Ajax. The Ajax response includes this:

[div class="vAvatar"]
[script type="text/javascript"]AC_VHost_Embed(3563894, 300, 200, '', 1, 1, 2302448, 0, 1, 0, 'MY_GUID', 9);[/script]

thought that might be relevant.
Unfortunately, no. This is happening in my local development environment. I cannot push out to the live site with the issue unresolved. Our QA environment is not public facing.
Hi Gil,

Yes setting localhost allowed a test project to work.
I will be using TTS. Is the domain resolved in the client (in which case localhost will work), or at the server (in which case I guess I would need to add my public IP address)?