I also find that it is the Winsxs folder that has problems with SFC.
When people post that the system file checker failed they send me their logs. When I read the log it says that the file it wants to restore needs to be restore from a file in winsxs but the file in winsxs is corrupt as well.
Which I dont think it is, Windows has to know how to tell if a file is corrupt or not, s hash or something, which means there has to be a list somewhere on the system. If I could find this list that points to the winsxs folder I might be able to see if it could be rebuilt, and thus fix SFC
Shane