A lot more great info.
Thanks for the picture, I'll put it to use.
I'm afraid the neck straightening tips don't help, as I play acoustic exclusively.
I'll keep them in mind for when I do get an electric guitar, however.
The strings I have on my guitar now are Darco acoustics tens...I had lighter electric strings on them before but I didn't like the sound as much. These are harder to barre than the last set, but when I do it right, they sound great.
Also, my problem isn't that my thumb just hurts, but when I play the chords, if I don't squeeze enough, I get sour notes...only when I squeeze hard enough to make the chord sound good does it hurt, so I'm sure I'm not squeezing too much (Unless I have improper form, which is possible.)
By the way, Nate, thanks for the site. \o/