Grades dont' matter in your first two years unless you failed a course and had to repeat it. Board scores at the end of your second year is where it's all at. Even if you had all C's, if your board scores are killer, program directors will still love you.
However, grades during your rotations are important, especially if it's in the specialty you want.
Err, never mind. Guess it was already taken care of in the other thread.