Wirelessly posted (BlackBerry8700/4.1.0 Profile/MIDP-2.0 Configuration/CLDC-1.1 VendorID/102)
I may be way off here but since when does sprint offer service in canada? If your friend is in an 'extended area' for sprint there is no guarantee they are going to receive any of your messages.
That is odd though if they were receiving them fine until upgrading. Is there a chance your friend is in a differen area now and thus on a different network?