Yes this happens to me quite a lot - seriously - it happens all the time - people just make judgements about me and dismiss me almost immediately as not being worthwhile.
I feel awkward when I am nervous and give off a bad impression - at least that is what I think. There is a few people at my job who wont even look at me, and they never have the entire time I have been there.
One girl I don't even bother with at all because all the times I have tried to initiate conversation with her she just shrugs off my presence. It's very rude.
But ultimately it comes down to them and their decision of how they see you. If someone isn't going to bother with you for whatever reason, it falls on them not you. It's frustrating and it hurts your feelings a bit (or at least it does mine, because if they took the time to know me, they would realize I am not all that bad) but you can only do so much when it comes to others reactions to you.