I have an older TiVo box (not a V6) and have recently started to notice errors when using On-demand.
When viewing any catchup but more noticeable on box sets, the connection drops out every 15 mins or so and I have to wait for the box to reconnect before resuming the program. The connection always resets and we have not noticed anything similar with the broadband recently. The set-up for the TV is exactly as it was when first installed by the engineer several years ago. There is a cable running from the brown box outside, directly to the TV point (it is not connected to the router).
I have also noted that the TV box has rebooted without notice a couple of times recently but not sure if this is connected in any way.