About a month ago I bought a FritzBox 7140 and retired my Vonage
service. The box is great and has so many features.

I also have a TiVo which is connected to the BT phone line, and makes
daily calls to download data.

Yesterday I noticed that the TiVo hadn't dialed up for quite some time
as the tv guide data had run out. I tried doing a test call which failed
on the dialing phase. I then disconnected the phone jack from the
FritzBox (not the ADSL one, just the voice BT plug), and the TiVo
connected fine.

I re-plugged in the phone jack to the FritzBox, and plugged a normal
phone in the jack that the TiVo normally uses, and it seemed to work
fine for voice calls as I tried dialing numbers. However, for some
reason it seems to interfere with data calls.

With a long telephone extension cable, I tried connecting the TiVo
directly to one of the FritzBox Fon POTS ports, and much to my surprise
it worked!

Any ideas? If I have to, I'll leave the wiring this way as it is
preferable to having two sets of DECT phones, which I had to have when I
had the Vonage box, but it's not ideal as the TiVo is some distance from
the FritzBox.