Yes, agreed - you can get water down an external antenna coaxial cable, so if you have one plugged into your TiVo, that's most likely to be the culprit. Well, unless you have your box installed under a sink :-)
Check for signs of water where the coax enters your home. If necessary (others feel free to comment on this bit) unplug your hub from the mains and unscrew the coax from the wall access point, check the connector for water or discolouring.
If water is coming in then it may have made its way to your hub too, I'd contact VM immediately and get your equipment checked for safety.
Edit: Just re-read your last post and I think you've already checked the entry point. Please contact VM now.
That's a bit of an unusual issue, I'm really sorry!
As apcyberax has said, you need to unplug the TiVo® as soon as possible and leave it unplugged. I've sent you a private message (purple envelope at the top right of your screen) so I can arrange for a technician to sort it out for you.
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