! Undefined control sequence.
l.278 \cit
Couldn't see anywhere I had \cit{reference} instead of \cite{reference} etc.
So I cut out the recently added text, saved to a new file, then added text paragraph by paragraph - the error has just gone.
As far as I can tell, the contents of the file.tex are the same.
Should I be thinking there is a problem with my OS or disk or memory or some such?
Thanks
Edit (update):
Another outside possibility - I had just copy pasted from the latex version of a book supplied to me by the author (yes, actually happened, I didn't just download a random file off the internet

Edit (further update):
Also noticed I had a few stray pdflatex processes hanging around which I have only just killed - might they have been involved in this?
Thanks again