ok, did some investigating and it does look like activator has been the culprit for springboard crashes when involved with iOS 4.2.1, however that was with the 1.4.1 version. we are now currently at the 1.4.6 version and i am having no issues whatsoever, although i remember with my 3G there were unexplained crashes and i had to remove activator temporarily..
so in the short you may want to verify you are at the current version of activator and or remove it until you can find a fix
remember, activator is part of sbsettings and you will lose this as well
After reading the article, it seems to me that "Comex saves untethered Jailbreak for iOS 4.3" is a false conclusion. Comex was asked whether the jailbreak will be ready for 4.2.1 or 4.3 and his reply was "Depends when 4.3 is out."
So how can one conclude that he's waiting for 4.3 when he clears says that it depends?