I\'m trying to use In-App billing:
mIabHelper = new IabHelper(this, BILLING_KEY);
mIabHelper.startSetup(new IabHelper.OnIabSetupFinishedListener() {
Had the same problem.
My device was rooted and ROM'ed with an older version of Google Market which did not self-update. You can verify your the Market/Play version by looking at it in the AppManager.
I actually decided to use another device, but I guess otherwise I would have to find a way to upgrade the Market/Play version.