I'm just wondering Fou..
Op says html is the same. Affected HTML is in an included file.. yet when copied out and pasted directly in it fixes the issue...
You reckon it might be an encoding problem like I had months ago? That led to all sorts of strange behaviours for me and it did different things on different servers too.
I could encode it as ansii on my system and all sorts of weird characters would show up but be fine on the remote server.
I'm just wondering if that could be the case here..