If AV was the only change then why not disable it and re-test? That assumes you're not in a corporate environment that won't allow that. Other option might be to try it on a pc that has not had the update, or get IT to roll it back for testing. I know of no reason why AV should cause lock violation warnings, but in trouble shooting sometimes the first approach should be to eliminate what recently changed.
The more we hear silence, the more we begin to think about our value in this universe.
Paraphrase of Professor Brian Cox.