We still have some old XP SP3 systems due to manufacturing processes and have been using SCCM 2012 without issue until we upgraded to 1511. The clients were upgraded through the automatic upgrade process. The Software Center won't launch from the notification area, get "Access Denied" error. It won't run from Start Programs either, getting error "Unable to open this Internet Shortcut. The protocol "softwarecenter" does not have a registered program."
Tried full re-install of the client but no joy. I can manually run scclient.exe and get the Software Center to come up, so I have a workaround. I know XP is no longer supported but that's not the reality for manufacturing machines. Thanks, Russell