There's one of 2 reasons why this happens. The TV guide is updated over the internet, so if your V6 has lost its 'net connection, that'll cause this. Check that's working by...
1: Using another internet-based service, OnDemand is a good one.
2: Following Home > Help & Settings > Settings > Network, and looking in the top-right - is there an IP address shown? If yes, choose "Connect to VM services now" at the bottom.
If the 'net isn't working, then how is your V6 connected to your homehub - Ethernet cable or wireless?
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