Just got back from the gas station.
It was just doing the same thing as this morning.
But, CraigM, I tried your little trick of pushing the little spring-loaded tab in with my key while pumping and it pumped gas just fine! After about a half tank I released the tab just to see what it would do and it allowed me to fill the tank the rest of the way without any problems.
The cap is original and factory, so I'm wondering if it's just worn or not seating properly.
What does that tab-button next to the filler do exactly? Open a vent?
Thank you guys again, and thank you Craig for your tip.
My mechanic is back logged, so will get a new cap from the dealer for now and see if it fixes it. If not, I'll have everything related to the vent system looked over for condition, starting with that vent valve (it seems to come up often in similar discussions).