I seem to have this problem: people often think I'm being insincere when I genuinely mean the things I say. I usually find myself having to convince people that I mean what I say when I do mean it and yet they have no problem accepting the things I say which I don't really mean. Not all of the time, but it's certainly a recurring theme in my life. 
skryche:
I experience the exact same phenomenon. But, then, I do ironically lie a lot.