false modesty, sure. Personally, I don't think false modesty is so bad; I know I'm kind of arrogant, and most people in my industry are kind of arrogant. It's irritating to deal with an arrogant person, so yeah, I try to tone it down. It's real common. 'I might be wrong' etc, etc... I don't see anything wrong with it; I'm just trying to be polite.
But if pointing out your own weaknesses looks like you are trying to deflect criticism, you are a long way from honesty.
actually... Once you have credibility with the person you are selling to? pointing out your own weaknesses, I think, builds a lot of trust.