Actually I experienced the same thing. I was using Aerobulk Bulk Cleanse which is a heavy duty type psyllium husk cleanse. Used it one night and I had the worse taste in my mouth when I woke up the next day and also had horrid breath for the entire day at work.
I brush/gargle night before bed as well so I couldn't understand how awful that taste was.
I may give it another try with another type Colon Cleanse and see if I have different results.