I know I'm clutching at straws here, but...
Has anyone who has had the ever-familiar 8506,421 error tried applying this update - and if so, does it appear to have solved the problem?
I'm reluctant to upgrade to 2013 (I'm currently using 2012, version 19.9.0.9) until I get some impression that the problem has been solved. Until then, and in the continued absence of any news or even just acknowledments from someone at Symantec, I am testing trial versions of competitors' products in the hope that I might just find something that's any good.