A few schools of thought.
Some have menioned that it means that the slingbox has lost its internet viewing settings requiring a hard reset of the unit forcing a setup from scratch. There are others that have solved the problem by doing a reboot of their router, modem and slingbox at the same time, not just the slingbox and yet some others have mentioned they have solved the issue with a new power supply ( thread below )
You mentioned you've been using it for years. All signs could be pointing at a failing power supply unit requiring a replacement