After latest firmware update update I was facing problem with connecting my Galasy S2 with PC/Kies using USB. Windows was unable to find required drivers when connected. I have tried all possible ways but unable to resolve driver missing error.
After lot of googling I have found out the main cause , phone USB connection mode was wrong. Followed the steps below and suddenly everything start working
1. Either install latest Kies OR just install compatible USB drivers
2. Before connecting the phone, open the keypad and dial *#7284#
you will see a menu for UART and USB.
3. Under USB, select PDA. If PDA is already selected, select MODEM and then back to PDA
4. Don't worry about USB debugging or anything, just connect your phone to the PC
Everything will work as it is intended to whether you use Kies, no Kies or just Mass storage