Hi,
I would like to point out something about the Errors and Warnings window. It shows both errors and warnings. Errors have a red stop sign like icon, warnings have a yellow triangle with an exclamation mark. In general errors are something you would worry about, and are most likely things which would prevent a render from being successful. Warnings are just warnings though, they are usually to notify you of something irregular happening but which won't necessarily stop a render from being successful.
It's the difference between "Things are seriously wrong and you should not go further" and "Something a bit funny is happening, but there shouldn't be any harm in carrying on. Just letting you know".
In this case the wording of the warning message is a bit unfortunate because it suggests it's an error.
Especially because the Tech Previews are still alpha quality software there are often warnings posted that are diagnostic tools for us, and not much use to you as users. The counter error is an example of this. For the final release we will try to minimise these sorts of things so that you only see useful errors and warnings.
Sonshine, the error you're seeing is the one being discussed here.
Regards,
Jo