US Visitor Entry for a Canadian

I'll try to keep this brief. Back in January 2007, I was not allowed to enter the US from Canada, and was required to sign a Withdrawal of Application for Admission form. My girlfriend is a Canadian student there, and I had planned to spend the following four months with her, already having spent the last four months there. Basically, I couldn't prove that I had sufficient ties to Canada.

Now, I would like to visit her for two weeks, after which I intend to travel to a conference in Scotland. My question is this: will possessing a return ticket, combined with proof that I will be travelling to and attending that conference, be enough to prove to a custom's officer that I have no intention of staying in the US? Complicating the situation is the fact that I am not employed, and am presently living with my parents.

I would appreciate anyone's assessment of chances.

Thanks.