This is an interesting one... I like to watch the Science channel which happens to be an SDV channel. Every few days, my TiVo loses the ability to tune this channel until I reboot it - displaying the message "This channel is temporarily unavailable", however during this time I can record the very same channel perfectly. I have two Premiere XL4's both exhibiting the identical behavior, so I know this isn't hardware related. I wonder if this will ever get fixed?