Win. Def. Update failure

Windows Defender version 6.1.7600.16385. Last def. update 1.139.124.0. failed and at the bottom of win. def. reads latest definition is 1.139.240.0, created on 19/10/2012. Checked for updates in Win. Def. and it said 'no new definitions or updates available'. I have been searching & can't seem to find this definition to download & install. The Malware Protection Ctr. shows a different set...