Richard 14 hours ago
this is what worked for me, dono if it will work for you
I've got similar problem with my SII, simply unplugged USB cable; on your phonedial *#7284# under USB select "Modem" mode then go back and dialagain *#7284# and again under USB select “PDA” mode then go back.
Now on your PC start Samsung Kies, then connect USB cable to your phone withoutgoing anywhere on your phone; just wait till the driver being installed on yourPC. The connection will establish between your phone and Kies. It worked withme and I hope it will be the same with yours.