CORRECTION:
No personal IRA if you are "eligible to participate for [a defined benefit] plan year ending with or within the tax year.:
But for a SEP, SIMPLE, SARSEP, or DC plan, an amount has to be allocated/contributed.
So it looks like I can contribute to my personal IRA _instead_ of my SEP... but not both.
Turbo-Tax, so far, is letting me contribute to both, and the chances of the IRA ever noticing are pretty small, I'd say... but best to play it safe, and best to be legal where it's clear what legal is.
