Pretty much as it states. There is no html after the byline in single post mode. I'm sure there's just an errant character somewhere or something, but can't get my head around it.
i'll give access credentials to whomever wishes to help, then they can post the solution here afterwards.
Buzu B answers:
I want to help, where can I see the code?
i've PMd you a login
Thanks for trying, I've just disabled the 30-odd plugins i had enabled, and it appears to be working again. so i'll just trial-and-error with the plugs to see what's causing it.