At one time or another I'm sure a few of us have had trouble with the boarder in both directions. As someone who visits the States frequently I'd have to say that 99% of the time I don't have a problem going in either direction. If you've got the necessary paperwork and have nothing to hide then it's usually not a problem. I, to be honest expect to be questioned when entering the USA. I'm the visitor so, I take it to be a given. Unfortunately, like it or not, 911 has changed things. All of us have to apply a little common sense when travelling these day's. Don't take it personally. I've got many American friends and I wouldn't dream of bashing them for any problem I may have at their boarder. They don't bash me if they encounter a problem on their visits to Canada.
Anyway's come back and enjoy some real Canadian hospitality