I've done abit more digging but only came up with one reported death from a woman and the cause was unknown though she was taking DMSO at the time - from the numbers of people (and animals) using it this would seem rare but there again who wants to die.... Do you know when the UC trial was written?
If nothing else the proposed harber weiss reaction is certainly interesting and makes me wonder -is the tissue damage caused by the OH radicals this may tie up with hydrogen peroxide being able to cause acute ulcerative colitis and additionally the damage could be reduced or eliminated by most anti-oxidants....