One darkhorse possibility would be Botulism. As the Type 1 Diabetic eludes to, I swear that the majority of these GI/IBS related conditions popping up like mad are eerily similar to what is observed in Gastroparesis, an autonomic nervous system complication, a condition that was once believed to be a death sentence strictly connected to Type 1 Diabetes, but is now rather considered to be more of a routine observation across the entire population .
The fascinating thing about the condition is that if such would ever be true, it all but confirms the long held belief by some that all of this goes back to the mind, one way or the other (AKA-stress).
Two of the lone exceptions would be Botulism, and Asperigillosis, conditions that would, unfortunately, tend to be on the back end of possibilities in the eyes of most doctors.
Also, one comment on the probiotics-be aware that medicine has begun to find several cases of lactic acid bacterial overgrowth in patients. While the merits are just behind probiotic supplementation, nobody truly knows whether or not this stuff ever actually makes it to the lower GI, where it is needed to be a friend to the body. The question, at that point, is what happens to this stuff if it doesn't make all the way down to the colon. Is it friend or foe if it is absorbed in the stomach?
At the minimum, in reference to this lactic acid bacterial overgrowth condition, it would seem that the lactic acidosis mystery might finally be solved. Symptoms of lactic acid b'al o'growth are GI distress, confusion, slurred speech, and possibly, dementia like behavior. The cure, evidently, is Antibiotics and sodium bicarbonate.