I agree with Strong330's description of the problem. However, as I have said, for me, this does not justify returning the saw. But that is a personal decision, and I can certainly respect it.
Lorax, I fully believe that you and other owners have a "normal" arbor. I mentioned this fact again this morning when I spoke with RIDGID tech support. They hold to their claim that all of the TS3650's have this weird design that they inherited from Emerson. They guy said they would be more than happy to send me another arbor, but it would be like the one I have.
Support said they have actually only had "a couple" of phone complaints about this problem. One suggestion they had, which others here have written about, would be to manually square up the blade or chipper that sits over the recess with the other blade(s), and then tighten up the arbor bolt. That seems like a rather unscientific workaround to me.
The dado blades all seem to at least lie completely perpendicular to the arbor thread (i.e. parallel to the arbor flange). I have not seen any problem with a blade tilting in the dado set, as the pressure of the collar or the arbor nut makes all the blades square. I may take some photos this weekend, and post them. This is probably not a huge issue, but it may save some future owners some time.
There are three kinds of people in this world - those who can count, and those who can't.