I've often been mystified WTF agents really mean when they talk about "voice" in a novel, especially when all they've given your book is a superficial two-page read. But I've been re-reading The Catcher in the Rye--the last time I read it was the summer between high school and first year of college--and there's no mistaking Holden Caulfield's--J.D. Salinger's--distinctive "voice." So I suppose I get it a little now.
More important, I'm loving reading it. I don't remember liking it that much when I first read it. But it's hysterically funny.