Thanks for your reply Nick,

I'm still stuck having this in my log files:

Jan 14 07:38:17 gateway pppd[7988]: Using interface ppp0
Jan 14 07:38:17 gateway pppd[7988]: Connect: ppp0 <--> /dev/pts/1
Jan 14 07:38:17 gateway pppoe[7989]: PPP session is 59734 (0xe956)
Jan 14 07:38:18 gateway pppd[7988]: Remote message: Authentication success,Welcome!
Jan 14 07:38:18 gateway pppd[7988]: PAP authentication succeeded
Jan 14 07:38:18 gateway pppd[7988]: Unsupported protocol 'IPv6 Control Protocol' (0x8057) received
Jan 14 07:38:18 gateway pppd[7988]: local IP address 81.205.120.246
Jan 14 07:38:18 gateway pppd[7988]: remote IP address 195.190.228.145
Jan 14 07:38:18 gateway pppd[7988]: LCP terminated by peer
Jan 14 07:38:18 gateway pppd[7988]: Connect time 0.0 minutes.
Jan 14 07:38:18 gateway pppd[7988]: Sent 0 bytes, received 0 bytes.
Jan 14 07:38:18 gateway pppoe[7989]: Session 59734 terminated -- received PADT from peer
Jan 14 07:38:18 gateway pppoe[7989]: Sent PADT
Jan 14 07:38:18 gateway pppd[7988]: Modem hangup
Jan 14 07:38:18 gateway pppd[7988]: Connection terminated.

I get the feeling that my ISP is closing the session as my system doesn't accept IPV6. If you look at the sequence it is like this.
Authentication - PAP authentication succeeded
System can't handle IPV6 - Unsupported protocol 'IPv6 Control Protocol' (0x8057) received
System gets IPV4 - local IP address 81.205.***.***
I don't understand this - remote IP address 195.190.228.145
ISP is terminating - LCP terminated by peer
Session terminited as
is recieved from ISP - PADTSession 59734 terminated -- received PADT from peer
Systems sends PADT and
does not accept any data
from this point - Sent PADT

Can it be the ISP is terminating the session as the offered IPV6 is not accepted?