I don't now if this is the exact problem you're seeing, but it may add some insights:
 When turning the box on, it may not display a picture, the picture may be solid green, a blue box may appear displaying an HDCP error, or multiple images may appear on HD channels
Cause: If you are using DVI or HDMI output, it may be because a proper HDCP handshake did not take place to allow the box to output the video to the TV. In this case, the DVI would display video for about 5 seconds then go blank or green. Occasionally, it may display video and put a big blue box saying there is an HDCP error (seen using a Sharp LC-45GD7U TV). On a Samsung TX-R2779H with a PII box and a DVI-to-HDMI cable, this led to multiple side-by-side images when watching a HD channel thru either DVI or component outputs.
Check to see if HDCP is enabled (obviously, while using component or other non-digital output).
If using Firmware 16.20 or later, check to see if the HDMI/DVI OUTPUT MODE is set properly.
This user (Doug) doesn't remember the exact sequence of events used to fix the problem, but it consisted of doing these things in a particular order after powering off the TV, the STB (fully powered off, as in unplug the power cord), and disconnecting the DVI cable:
Plug in STB
Turn on TV
Connect DVI cable
Power on STB
Note: After a few tries of various combinations, I got the DVI to work fine and the status display showed HDCP was enabled.
If you constantly have HDCP handshake issues between a PI/PII box and an HDMI display thru a DVI-to-HDMI cable or adapter, replace them with a PIII box and a pure HDMI connection. On the Samsung above, this not only resolved the issue, but also improved analog picture quality and added digital sound. (Many cable companies in the United States will "swap out" leased PI/PII boxes for PIII boxes, if available, at their local offices for no charge.)
Cause: The Motorola STBs with certain firmware revisions are known to have issues with HDMI/DVI repeaters, including most home theater receivers.
Remedy: None. Motorola fixed the HDCP handshake to allow repeaters as of Firmware 12.35.
Also see: http://en.wikibooks.org/wiki/How_to_...orola_DVR/Bugs