Had a problem with downloading a spreadsheet when some of the entries had characters with accents or other symbols. Fix:
csv << ["#{user.username}", "#{user.fullname.force_encoding("utf-8")}", "#{user.institution}", "#{user.day1}", "#{user.day2}", "#{user.lunch}", "#{user.dinner}", "#{user.created_at.to_s(:month_and_day)}"]
Just add .force_encoding("utf-8") to the field causing the problems. Might have to do this in a bunch of places, but luckily for us, it was just in one.