The new apn worked fine for a wired tether! (HTC Aria, 2.2) Have you seen an invoice from AT&T? Seems like I heard they are cracking down on folks using "free" tethering apps. I realize this one was from AT&T,but I've been on the phone for hours over this issue. Last Thursday (11AUG11), AT&T called and said this had been through 2 different teams, but they didn't know how to enable tethering (without moving to AT&T plan with limited data.) It was now with the "Alltel transition team" to figure out how to tweak the carrier-side software to permit it.
Good luck. I wound up ditching ATT because I was tired of dealing with customer service. I don't think they even trained most of the customer service reps before putting them on the phone; It didn't matter why I was calling, they would keep transferring me, keep me on the phone for hours, promise a call back but never call, and worst of all they never found a solution to anything after wasting all that time.