I have used Iodophor exclusively for 10 or so years. Professional food service kitchens use it all over. Medical facilities use it. I'd look somewhere else for your problem. Iodophor definitely works.
How long did it take for the yeast to take off? Did you use a starter? Did you rack to a secondary? What was the primary fermenter? Did you take the keg apart and thoroughly clean all the parts before using? Like the posts and everything? Did you taste it when you racked to secondary and how did it taste then? Did you chill with a counterflow chiller, and, if so, what is your procedure for cleaning and maintaining your chiller?
These are some of the things I'd be asking myself based on past infection problems. Iodine definitely works, unless you diluted it waaaaay too much, so if you want to get to the bottom of the problem, I'd look elsewhere to avoid it in the future.
Sorry about your batch. That's always a bummer
