Does anybody have any similar experience as I'd felt very secure with avast! HE 4.1 up until now, especially as avast! frequently runs automatic multi-updates in a single day to my always-on broadband connection?

Its a known fact Avast is not the best at detecting trojans. But with every update it gets better at it. If you wouls like this trojan added to the database send it in to them virus@avast.com