RECAP: flex_sdk_3_192625
Take this example adding an itemRender to a List with itmeRenderer not in source root a file foo.mxml that's in the folder com\blah\blah\view\foo.mxml has element <mx:List id="myListNav" itemRenderer="com.blah.blah.renderer.ListRenderer" /> ListRenderer.mxml is in in com\blah\blah\renderer\ListRenderer.mxml throughs a comiple error works fine with M4Beta3 Just in case anyone else needs this info. (I know nightly are not for general use, and this is the kind of stuff that happens)