pppoe grinds to a halt

[Donn]

Hello again,
I have (yet another) problem with my Internet connection.

My WISP has recently switched to pppoe. I ran pppoeconf and it 
generated /etc/ppp/peers/dsl-provider, all good. I use pon dsl-provider to 
connect and that works too.

The mystery is this: after a time (that varies) the tap seems to close and I 
cannot surf or get mail. The ppp0 interface is still up but the taps are off.
I 'poff' and 'pon' again and instantly the flow is back.

What could be causing this? Any clues?

/d