I just had this exact same thing happen to me today. Last night, feeds on 2 of my cams went out unexpectedly. I restarted BI and got this message. Rebooted the PC and same thing.
EDIT: Uninstalled. Fresh install. Imported my backup file. Everything is back to normal. Wish I knew wtf happened!
This is the most hated camera in my house but I found that the video setting H.264 HW decode = "No" brings up a stream. Any other choice there renders it disabled again.