You might have seen an issue with the patch KB974417 where after installing patch KB974417(http://support.microsoft.com/kb/974417), it gets re-offered by WU. I found that after installing the patch the files (mscorlib.dll,SOS.dll,mscorwks.dll,mscordacwks.dll) are NOT updated on the system. The file version should upgrade to either 2.0.50727.3603 OR 2.0.50727.4062

It was found that a bad baseliner that prevented this KB from being installed correctly. I was able to reproduce the issue after installing KB952883 (containing the bad baseliner) and then KB974417. This issue is fixed by installing the hotfix KB975954 mentioned in the article http://support.microsoft.com/kb/2262911