I am pretty much convinced it is a RIM issue. Unless it is something in between BIS and Yahoo like a network problem. BUT the sync issue we are seeing, which is really what is irking me, is certainly not a result of a network problem. It is like the lines are crossed or someone put the 'flux capacitor' in backwards (or would that cause something far worse
I did research on Plus vs. free Yahoo accounts. RIM specifically stated that two way sync is available for all Yahoo accounts. So that rules that out too, as mentioned.
I did not bother calling AT&T as I did not want to go thru the same steps anyone here or RIM's support would tell me to do. What's the point other than maybe getting through to someone? Plus, they'll eventually tell you to call RIM. And RIM will tell you to call your provider.