I understand that you are having some issues with your Slingbox virtual remote control since you are no longer able to use it to control your Slingbox and the attached set top box.
Most of the times, this issue will come up if the IR Blasters are out of range. With this in mind, I encourage you to check the following links. They will allow you to determine if the IR Blasters are working fine or not:
Hope this helps.