At the login screen, look in the bottom left corner for very faint "Session Type: (I think). Select KDE3. And, yes, some KDE4 components are installed automatically because some apps need them (I think ARK and some others). No sweat. If you chooose 3.5 at the login screen, you won’t even realize that some of the apps also work under 4.x
That may be true but if kde 3.5 is selected then the default boot should be kde3 not kde4!
The usb problem is new, it didn't happen with any of the betas or rc1.