Usually when you see a screen roll that points to the cabling. Either the Video cables are going bad and need replaced, or they need to be unplugged and plugged back into the Slingbox tightly. If that does not work, try uninstalling and re-installing the SlingPlayer application; you will not be charged to do so. Just incase you are unfamiliar with uninstalling an application from your device, here is an article that will walk you through it:
Hope this helps!!