Our screen (not the TV screen) goes blank when we change channels from an iPad, iPhone or Macbook Pro (using both Safari and Chrome).
We can't recover the video until the device (iPad, iPhone or Macbook) app or browser is restarted, and sometimes we have to restart the actual device to get the video back.
We do not use an HDMI cable from the Slingbox to the cable box.
Some more information about the issue with changing channels.
I can change the channels in the range of 02-48 (basic cable). Once I change the channel to any hi-def channel such as 603 the screen goes blank and can't be restored without shutting down the app or browser or sometimes restarting the device.