Originally Posted by chucky

Ok so I've ridden about 150 miles at 100 psi since I switched to a wider tube and have had no flats. I also checked the tubes I was using and the original tube that was punctured on the road was CST (that's the brand) 20x1.5-1.75", then the next 9/10 flats were with the 3 different XLC 20x1.25-1.5" tubes (purchased brand new about 6 months ago), and the flats finally stopped when I put in a vintage Kenda 20x1.6-1.9":
So it was the tubes!

Not the rim tape.
Not the rims.
Not the tires.
Not the spokes.
and NOT user error.
So unless XLC tubes are total crap it appears the problem was simply that the tubes were too narrow and became too thin and fragile when they were inflated to fill the 2" wide tire (contrary to what it says in pretty much every bike mechanic book or class in existence).

And BOY am I happy I didn't listen to some of you knuckleheads and buy Velox rim tape because if I did then I NEVER would have solved the problem and ended up helpless, ignorant, and suckling at the teats of the corporate overlords for the rest of my life (just like some of you). And now that I discovered how unreliable buying inner tubes from professionals can be I might just try my hand at making some of my own from a rubber tree. After all, how would I have stopped the flats if I couldn't get the right size?

In any case thanks to everyone who took a shot at helping me (even the helpless knuckleheads).