Could not install MTP USB Device with Samsung Galaxy S

I am running Windows 7 when connecting my Samsung Galaxy S. I used Kies to connect. When I first connect my Galaxy S, it automatically installs but the MTP USB Device failed to install. The effect is I could not connect my Galaxy S to my PC. What is causing this?

Device driver software was not successfully installed
Please consult with your device manufacturer for assistance in getting this device installed.
Samsung Android USB Composite Device Ready to use
Samsung Android USB Modem Ready to use
MTP USB Device Failed
