Have a Slingbox PRO HD. I've upgraded to the latest firmware.
With the slingplayer for both android phone and web browser, it flashes every 2 seconds or so and then after each flash the picture moves down by a scan line so after a few seconds there's a horizontal bar across the screen.
This does not happen when I'm at home and not having to go through a comcast cable modem to the internet.
Is comcast doing something to throttle back the signal?
+1 This is happening to me as well. I have FiOS at the location of the box and am having the same issue on the WD Live, iPad app, and viewing in Mozilla. I read somewhere that a firmware update will fix this, but my slingbox has the latest firmware.