and again it seems to be a problem with the template and not the XML itself :/
The same thing happened to me once. Found that a plugin or something had fucked up my headerinclude. Might want to start there.
Maybe replace your current with a fresh copy of the headerinclude template?
I did that before.
It didn't work.
I looked at the templatemultiple times and I saw no differences. :/
I couldn't tell you the exact problem without seeing your things, but I won't ask of that.
I'm willing to give you a temp admin account so you can look into it. I have backups of everything. I don't mind. If you can help I will love it
I wouldn't have time tonight as I am about to get off. If you still need it fixed tomorrow I'll look into it. But yeah, what aoki said, it's a messed up JS issue.