I had to register just to say "Thanks" guys, I spent pretty much all of last Friday trying to "fix" SCCM when it mysteriously broke.
Uninstalled KB2835393, KB2804576 and KB2840628 - rebooted the server, and now both the SQL errors in the statesys.log and the package issues are fixed.
When trying to add/modify packages I got an error saying something about "failure generating lantern", now behaving.
So thanks very much!