'AdobeAn' is undefined:Animate file not loading in Internet Explorer for client, not replicable

Solved –

Our server was incorrectly blocking ".*map.*" instead of "\.map$" in an attempt to stop external people loading JS/CSS .map files. Once this had been updated, it fixed the problem.

Thanks for everyones help.

that's usually caused by a major error like mismatched braces in your code.

I'm pretty sure you should be investigating that "Unspecified error" that happens first.