J.B.
Have you tried seeing a developmental pediatrician? My 4-1/2 year old daughter has had similar behavior for at least the last 3-1/2 years. Discipline of various kinds have NEVER worked for her either. Finally her developmental pediatrician diagnosed her with sensory integration dysfunction and emotional dysregulation and referred us to occupational therapy. Basically, her nervous system becomes overloaded with sensory stimulation that she can't organize (and determine which input to ignore, like the sound of rain). She becomes overwhelmed and acts out. Often I have no idea what set her off. Her socks are twisted in her shoes? The dog bumped her and she wasn't expecting it? The sound of the hairdryer? A smell she doesn't like? I had pleaded for help from this doc before as well as her regular pediatrician, etc., but until she witnessed one of my daughter's "episodes," the problem had been mine - a problem of my expectations, experience, consistency, ability to discipline, etc. My daughter now sees and occupational therapist twice a week and has made remarkable progress. The OTs also work with Asperger's kids, which someone else mentioned. Email me if you are interested in the doc (Worcester) or OT (Westboro) my daughter sees. You could also read "The Out-of-Sync Child" by Carol Stock Kranowitz as this book has excellent descriptions of what sensory issues "look" like.
Good luck! Whether the ideas I suggested are at the root of the problem or not, I know how exhausted, frustrated, and embarassed you are.