The Patch KB 974417 http://www.microsoft.com/downloads/details.aspx?familyid=491874d4-5eea-4545-9b7d-3861857c862e&displaylang=en might fail to install with an error message "The upgrade patch can not be installed by the windows installer service because the program to be upgraded may be running or the upgrade patch may update a different version of the program".
As per http://support.microsoft.com/?kbid=974417 basically this patch upgrades the files (mscorlib.dll,SOS.dll,mscorwks.dll,mscordacwks.dll) version to either 2.0.50727.3603 OR 2.0.50727.4062 I found that the system already had the patch KB976569 http://www.microsoft.com/downloads/details.aspx?FamilyID=8b9e4bb3-5a33-443e-bb09-9f9e506db519&displaylang=en installed on the system. As per http://support.microsoft.com/?kbid=976569 basically this patch upgrades the files (mscorlib.dll,SOS.dll,mscorwks.dll,mscordacwks.dll) version to either 2.0.50727.3607 OR 2.0.50727.4413
So the conclusion is that we already have a higher version of DLLs (KB976569) on the system so it wouldn't allow you to install lower version of DLLs (KB974417). Hence, you really don't need to install the patch KB974417 on the system where you already have (KB976569).
There's a revision we released to revise the WU detection logic so that Kb974417 doesn't offer if the other KB is installed already. You would need to re-approve the newer revision in WSUS then the issue should be resolved. WSUS administrator receives all revision and you just need to go to the same KB(974417) and approve the newer version.
Here’s an example screenshot. Note that there’s a message for the KB saying “There’s a newer revision of this update available”. WSUS administrator just needs to approve it as usual.