Interesting. I'd be curious to hear if anybody else has noticed this.
sfgoat, you've never tasted this characteristic in your other brews?
EDIT: As far as brewing with darker sugars, I've recently moved to unprocessed sugars. Using a dark raw sugar instead of regular brown sugar might really help. I'll try it that way this year to see if that makes a difference.
I've never noticed it in another brew but this is the only time I've used brown sugar. I'll try it again this year without it and see.