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.
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.