I had that problem and I did what Sean suggested
After you reboot, the VOOM guide comes up, touch FAV list button on the remote. Another screen will come up saying " downloading PG information wait until it disappears..." after this screens goes away, turn off stb and turn it on using the remote control. At this time you will have all your channels and picture but no information in the PG. Let it way another 15 minutes to download the rest of the data