open your Windows Device Mgr, On the menu >>>>VIEW >>>>> Show Hidden Devices
Disconnect all USB devices you might have connected, then under Universal serial Bus, Delete ( Uninstall ) anything in there.... Then reboot and let Windows re-detect all your devices and install the Samsung drivers new :
Drivers for ( only one, depending on the Win7 version ):
32-bit Windows : http://db.tt/eGN4acLK
64-bit Windows : http://db.tt/IlIkQ4BV
Let us know if it worked !!