Just found relevant issues/help in this thread:
http://forums.oztivo.net/showthread.php?t=1470
I think an older version (around 30Nov2006) of nic_config_tivo may have created a blank ppp-options file. Apparently that has been fixed in recent (2007) versions of nic_config_tivo. 'update -y' at a bash prompt should get it...
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