Thank you for contacting Slingbox Forum. I am sorry you are having the white video screen. Is this happening on the computer and any mobile devices?
Have you tried to change out the video cables entirely? You may want to check and see if those cables work with another video source to confirm the ports on cable box are working to send out the correct video and the Slingbox ports can accept the video signal. Here is a link to assist you with general video issues:
Hope this helps with your issue!
Have a great day!
Sling Moderation Team