We've run into an issue with my roomie's Cannondale F700.
It has Avid BB7's (mountain version) on it. The rear caliper arm doesn't retract all the way after the brake is applied, this leaves the cable loose enough to settle against the top tube. It doesn't regain tension until the caliper arm is manually reset.
We used Park Tool's guide to adjust them initially, but saw no mention of this.