I've had really good luck using Krud Kutter to clean urethane grout film and mineral spirits for acrylic grouts. Krud Kutter has a very low odor, But I've heard it's difficult to get in Canada. You can also use Goof-Off, but it has more of an odor. And we all know what mineral spirits smell like! use only where in well ventilated areas.
Remember to work in a small area at at time when grouting!