Fannie Mae has issued Selling Guide Announcement SEL-2010-11, which clarifies that lenders are not required to obtain a second credit report just before loan closing.
http://www.fanniemae.com/newsreleases/2010/5126.jhtml;jsessionid=A3YIQROLNZ5RHJ2FQSISFGA?p=Media&s=News+Releases
https://www.efanniemae.com/sf/guides/ssg/2010annlenltr.jsp?from=hp
https://www.efanniemae.com/sf/guides/ssg/annltrs/pdf/2010/sel1011.pdf