Hey all
I too had been having the same problem described by many others in the last few weeks. Running Internet Security on a 32-bit Win XP Pro (SP3) machine, using Outlook 2007.
To be honest, i notified Avast! of the problem yesterday and someone called Michal was VERY fast in responding - thumbs up!
In my case, following an earlier poster's advice, i did this:
Without installing the recommended beta version, just by turning the Avast COM add-in off on my computer within Outlook's Trust Center off. While on the Avast! Screen I have all the bits installed and running as normal.
Anyway this has solved my problem (of turning valid messages into SPAM as well as changing ALL messages in my Sent box into the last "Junk" email subject line - as described by various others on the forum here.)
Somehow disabling that add-in seems to be the solution, though I guess this also means that Avast! Is not really scanning my emails properly for potential SPAM - correct?
JPH