A couple of years ago, when I hadn't gotten mileage posted to my Aeroplan account six weeks after the flights, I called the Aeroplan center, and was lucky enough to get a very helpful, friendly, Aeroplan representative. After explaining the situation to her, she asked for the ticket numbers on the bottom of the ticket coupon (passenger copy), and said that the mileage would be credited immediately. It was in my account the next day, saving me from sending in the tickets and boarding passes. This may be the exception, rather then the rule, but it worked. Maybe I just got an extremely helpful rep, but its worth a try. In any case, I'd call UA first to see what they say about the delay, then give AC a call to see if they can speed up the process. Proves again the importance of saving all tickets and boarding passes until mileage is credited.
Good Luck.
bj-21