Here is the rule from
http://www.ncaa.org/library/rules/2007/2007_football_rules.pdf
SECTION 4. Opportunity to Catch a Kick
Interference With Opportunity
ARTICLE 1. A player of the receiving team within the boundary lines attempting to catch a kick, and so located that he could have caught a free kick or a scrimmage kick that is beyond the neutral zone, must be given an unimpeded opportunity to catch the kick (A.R. 6-3-1-III, A.R. 6-4-1-V and A.R. 6-4-1-X).
a. This protection terminates when the kick touches the ground or is muffed by any player of Team B beyond the neutral zone (Rule 6-5-1-a) (A.R. 6-4-1-IV).
b. If interference with a potential receiver is the result of a player being blocked by an opponent, it is not a foul.
c. It is an interference foul if the kicking team contacts the potential
receiver before, or simultaneous to, his first touching the ball (A.R. 6-4-
1-II, III, VII and IX). When in question, it is an interference foul.