<!–more–> produces a <aid>-tag

I have a little problem. I’ve noticed when I validate my site that it gets errors where the <!--more--> -tag is, it produces <aid>-tag instead, I assume that there’s missing a space between ‘a’ and ‘id’. See it here: Link for validator.
I have re-uploaded the whole includes folder and I have even looked through post-template and the theme coding but no luck.
Does anyone know what could be wrong?
I didn’t have this error before I upgraded…