From the infomation on the exetel forum you could try the following:

cat /proc/sys/net/ipv4/ip_no_pmtu_disc
echo 1 > /proc/sys/net/ipv4/ip_no_pmtu_disc
cat /proc/sys/net/ipv4/ip_no_pmtu_disc

The 1st line should give a result of 0
The 2nd line give no result
The 3rd line should give a result of 1

Now type reboot to reboot the tivo and see if it works.

Peter.