I was just thinking that another cause of the oxidation (especially if it wasn't severe) could be the bottling from the keg. Without a counter pressure set up, oxidation is a real risk. You could try being a bit more careful, and using a beer gun, or using the "we no need no stinking beer gun" method from this forum (Biermuncher posted the link) but to make sure that co2 is present when bottling.