In-app purchases won't work
I have 2 iPod Touches, a 2nd-gen and a 4th-gen. I used the 2nd-gen, and my wife used the 4th-gen. Both were attached to the same Apple account. She could make in-app purchases, but I could not—whenever I tried, it either gave me some kind of error or just failed with no explanation. I could never get it to work.
Recently we traded iPods, restoring our stuff onto them from backups. But it's the same situation—she can make purchases, and I can't, even though we're using the other iPods now.
This leads me to believe there's something messed up with my iPod software somehow. It can't be my Apple account, because both iPods use the same one. And it can't be the hardware, because now we've switched. I'm really at a loss for how to fix this.
Just FYI, restrictions are not enabled on my iPod. It is also not, nor ever has been, jailbroken.
iPod touch, iOS 5.1.1