Paypal MPL iOS error

I am trying to integrate the PayPal MPL library into an iOS app. I have a UIViewController that is creating the PayPal button like so:

- (void)viewDidLoad
{
    [PayPal initializeWithAppID:SANDBOX_API_KEY
             forEnvironment:ENV_SANDBOX];

    UIButton* paypalButton = [[PayPal getPayPalInst] getPayButtonWithTarget:self andAction:@selector(checkoutPayment) andButtonType:BUTTON_294x43];
    [self.view addSubview:paypalButton];

    [super viewDidLoad];
}

The app prints the following error message to the console a second or so after opening the ViewController.

Checking Error********************
Posting Error: 2147483647
DEVELOPER ERROR: This app isn’t using a supported version of the PayPal library.

I can't find anything about this error on Google, so here I am. Any ideas on how to fix it?

I am using xcode 4.5 and iOS 6 beta to test, and the 1_5_5_070_iPhone_DevelopersPackage version of the MPL library (the latest one on the website).