When longtime Denver Post music writer G. Brown resigned his position last week after being accused of plagiarism in a review, he chalked the copied portions of the review up to sloppiness and the pressures of the daily deadline. But now, it appears that an even larger chunk of the review that cost Brown his job may have been pilfered from a New York Daily News story, and the whole incident has caused the Post to rewrite its internal ethics policy, to the dismay of some staffers.