Recently, some customers reported that after they ran Windows Update and installed Yi Ruan Bluetooth driver, the bluetooth devices like mouse or keyboard was not working any more.
Resolution:
Follow the steps to roll back to the old driver, :
You must be logged on as an administrator to perform these steps.
Open Device Manager by clicking the Start button , clicking Control Panel, clicking System and Security, and then, under System, clicking Device Manager. If you're prompted for an administrator password or confirmation, type the password or provide confirmation.
Double-click the category containing your device driver, and then double-click the name of the device that you want to restore to a previous driver version.
Click the Driver tab, and then click Roll Back Driver.
If you are logged on as a standard user, the button will be dimmed, which means it's unavailable. You must be logged on as an administrator to roll back a driver.
More details are at http://windows.microsoft.com/en-US/windows7/Restore-a-driver-to-its-previous-version.