iPhone 3G will not fit in old dock. According to an Apple store employee, old iPhone docks will not fit the iPhone 3G, so you should purchase a new dock for the 3G iPhone. “the iPhone 3G is shaped differently and doesn’t fit in the same dock.”
(via iphoneatlas)
I was actually looking around for a forum post on this issue, but stumbled across your site on Google!! I’m actually quite interested so will keep an eye out for updates