PPPoE/PPPoA connectivity problem

[Augie]

hello ubuntuers, 

I installed Ubuntu 4.1 on one PC. My modem-router uses PPPoE/PPPoA
method for PPP packets in Ethernet.
I can connect with my ISP using a standard Ethernet card and
Ethernet-based DSL modem only after editing the resolv.conf file as
below everytime :

root at planet:/home/jupiter # cat /etc/resolv.conf
nameserver 123.99.222.70
nameserver 123.99.223.70

I save and exit the file but it timesout after some time. Everytime I
switchoff or reboot my PC, the modem-router the /etc/resolv.conf
changes to the old values. I dont know why that happens, and root has
r-w-x permissions too.

Some commands I tried show this  (if its useful, as I cant make any
sense of this) :

root at planet:/home/jupiter # ifconfig -a
eth0      Link encap:Ethernet  HWaddr 00:0A:2A:0B:5D:01
          inet addr:290.260.1.2  Bcast:190.260.1.255  Mask:255.255.255.0
          inet6 addr: fe80::20b:2bff:fe0c:5c01/64 Scope:Link
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:2 errors:0 dropped:0 overruns:0 frame:0
          TX packets:24 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:1180 (1.1 KiB)  TX bytes:6876 (6.7 KiB)
          Interrupt:209 Base address:0xa800

lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:57436 errors:0 dropped:0 overruns:0 frame:0
          TX packets:57436 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:4217726 (4.0 MiB)  TX bytes:4217726 (4.0 MiB)

sit0      Link encap:IPv6-in-IPv4
          NOARP  MTU:1480  Metric:1
          RX packets:0 errors:0 dropped:0 overruns:0 frame:0
          TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:0 (0.0 b)  TX bytes:0 (0.0 b)

root at planet:/home/jupiter # sh /etc/netstart
/etc/netstart: /etc/netstart: No such file or directory

root at planet:/home/jupiter # netstat -rn
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface

Is my PC DNS client since I dont have a static or dynamic IP address ?
I read that in some documentation.

Now to allow users to access the internet how can I set permissions ? 
Being new to Linux I am not very good at command line so just point me
to some resources please or some solution as editing the resolv.conf
file every hour is not fun at all :(
I hate to say this but the connection works like a charm on Windows,
so I know its not the hardware or ISP problem. Finally I dont know if
the problem is with /etc/resolv.conf file or  PPPoE/PPPoA .

Thanks, 
Augie