Check to see if the TiVo output format is either "native" or 480i. You don't mention which model she has, but my Samsung 4665 does NOT support 480i over HDMI for some silly reason. I would strongly suggest you switch to either 1080i or 720p FIXED (match the native resolution of the set). You may have to use component or composite video out into the TV just to make this change. After that, your HDMI should be good to go.