Error usps shipping to Canada

My customers are getting an error if they are trying to have their order shipped to a Canadian address. It will say during step 1 of checkout:
An error occurred with the USPS shipping calculations.
If you prefer to use USPS as your shipping method, please contact the store owner.

I think this may be the only country that is giving the error. How would I go about correcting this?

I am using v1.2.7

Thanks!

You probably have deselected the types of shipping methods available to get to Canada, from within your USPS shipping module. Try enabling the global-express etc options

Also, check your USPS Shipping Module code:
/includes/modules/shipping/usps.php

There have been changes over the last year on the settings around lines 99-108 These must match exactly:

    $this->intl_types = array('GXG Document' => 'Global Express Guaranteed Document Service',
    'GXG Non-Document' => 'Global Express Guaranteed Non-Document Service',
    'Express' => 'Global Express Mail (EMS)',
    'Priority Lg' => 'Global Priority Mail - Flat-rate Envelope (Large)',
    'Priority Sm' => 'Global Priority Mail - Flat-rate Envelope (Small)',
    'Priority Var' => 'Global Priority Mail - Variable Weight (Single)',
    'Airmail Letter' => 'Airmail Letter Post',
    'Airmail Parcel' => 'Airmail Parcel Post',
    'Surface Letter' => 'Economy (Surface) Letter Post',
    'Surface Post' => 'Economy (Surface) Parcel Post');