Hmm... Wonder if this a HDMI / Video issue...
First, did you try a different HDMI cable and a different port on the TV (or preferably a different cable on a different TV)? Cables rarely go bad, but swapping cables is a quick check. If you have a different TV in the house (or a computer monitor with HDMI), that's also a relatively quick check.
Assuming that doesn't work, do you have any ability to check audio only? For example, an optical cable to hook to an AV Receiver, or an AV cable that could you use (I forget if those come with the BOLTS, but I think they are a 3.5MM to RCA). I know you won't see the picture, but you'd hear the sound effects when you hit the TiVo button on the remote.
If you hear the initial sound, then the unit is working but has no picture. While I suppose that could be something power supply related (since any noise / power shortage on HDMI could cause handshake issues), some people have had HDMI issues on Bolts. So I would check the power supply first, and if that doesn't work, then seek a repair from TiVo. NOTE: I don't believe the HDMI port is repairable, so you might end up calling TiVo and putting your old drive back in if they offer some type of exchange...