In all seriousness, no, having a black friend does not make you not racist. Those of us with pets love them, but most of us probably see ourselves as superior to them. In the same way, you can like a black person, but still believe that he's a member of an inferior race.
My black friends call me their "-blam!-" so I think that makes me one of them. Therefore I can't be racist, because you can't discriminate your own race.
Racism is, more or less, an ideological perception of race, and so by virtue of thinking in such a way, you are then considered a racist. Much in the same way you are considered a Democrat for having similar ideals, or Christian for having similar beliefs.
Exceptions do not eliminate the overarching concept at hand, and by having an African-American friend does not constitute a way of eliminating the possibility of the individual holding prejudiced thoughts, especially when the concept of "racism" is not limited to just one race.
I see bigots on here all the time trying to downplay their xenophobia by screaming the "I have a black friend" card as if it suddenly invalidates their disgusting conjecture.
I swear you cant just "be" a racist, or not one. You might be fine around blacks, but hate Chinese, and thus still be racist. Everyone's probably slightly racist, just to different people.
While it doesn't make sense that you'd be racist towards other black people, you could still easily be racist towards other groups.
So, yes. You can still be racist with a black friend.