I can't comment on 3G bur I simply plug in the mouse's wireless USB and off it runs! Try plugging it in with the tablet switched off and see if it finds it when it is loading the OS. Also try switching on 3G after it loads the mouse (if it does load it).
I too cannot comment on 3G, but I have been able to use both a wired USB mouse and a wireless one on both my wife's Archos 101 (Gen 8) and my Acer A500 Iconia.