I just got a Roku for one of the rooms of my house. The Roku will do just fine up setting up until it downloads the latest update. After the update, the Roku restarts and shows the Roku bootup screen, then immeidately cuts out, and the picture never comes back. I've tried this with 3 HDMI cables and 2 TVs and still having the same problem.
Thanks for letting us know about the issue you're seeing. If you can, try plugging the device into a different TV to see if you experience the same issue. If the display comes back, try changing the option in Settings>Display type from 'Auto' to something manual, such as 720p or 1080p, and then plug the device back into the original TV to see if this restores video output.
Please send me a private message with your Roku account email address, the serial number of your Roku player from the bottom/back of the device, the specific make/model of TV and/or A/V receiver that the player is connected to when it experiences the problem. I'll help investigate this further and see what else we can recommend.