Seriously, read it again. Telling the coach to keep an eye on his players is not the same as having them investigated.
It tells me that the Duke lacrosse team was out of control frankly. The fact that they were so bad that it came to the administration's attention (generally hotshot sports guys get away with murder) and the coach got a warning means it's serious.
Also, I remember reading in either SI or ESPN that the reason that the lacrosse season was suspended was more cumulative than anything else. The rape allegations and rowdy party were the last straw for the administration.