IMac Ethernet: Cable YES but DSL NO, any help?

Question

Looking for help on internet connection problems with new iMac. I've posted this issue under a topic that is now marked as solved, however I do not see the solution.
I have a new 17" iMac intel. It hasn't been opened so it has the 512 MB RAM it came with, no other alterations, only added one application that's required for the business where this will operate.
I was able to easily and successfully connect to the internet using a high-speed cable modem (Rogers in Canada).
The computer is being used in a location where cable is not an option, so high speed DSL (Bell Canada) was chosen. I have not been able to successfully connect to the internet with this service.
Here's the steps taken:
1. Hooked up Speedstream 5200 modem as directed, followed set-up steps for TCP/IP as directed. Tried to connect. Connection times out, says there is no connection. When the system or modem is rebooted the lights on the modem suggest everything is working fine, according to the manual. There is also a green 'light' next to Built-in Ethernet in Network Preferences. This 'light' only goes red after trying to connect, and the ENET light also goes out on the Modem.
2. Spent a fair amount of time on the phone with Bell. Tried connecting using PPPoE without success. Tried to "configure the modem" by connecting to 192.168.2.1 but could not. Tried connecting without a splitter, made sure that phones on the line had the filter applied, all the standard issue steps from Bell. They could only suggest it was a Mac hardware problem. They were not swayed by the fact that I could easily connect using cable modem. Their Mac support is minimal at best.
3. I've tried deleting the Built-in Ethernet as suggested elsewhere so it is 'rebuilt'. I've installed 10.4.6 Combo update (twice) and it hasn't helped. I've pinged 127.0.0.1 (as suggested elsewhere) without packet loss which I've read likely suggests it isn't the systems ethernet port.
I've not applied the recent firmware update as I don't want to use windoze on this machine, but will apply it if it'll help in some way.
Can anyone suggest the next step. Am I missing something here? I've been troubleshooting through various forums looking at my options, thus some of the steps above. All the usual maintenance steps are taken (repair permissions, remove other devices, etc.).
I've been able to successfully set up the internet on many a Mac system since OS 7, but I'm no networking genius, things just worked as they were supposed to.
Any hints, tips, resources, links or direction would be helpful.

Answer 1

are you getting an ip when set to using dhcp? if you are supposed to configure your modem using dhcp, make sure the "connect using pppoe" option on the pppoe tab is unchecked (make sure you have "show" set to built in ethernet) you should be able to type in the gateway ip address listed into a web browser to access the setup screen. then go from there. if you dont see one you might try clicking the renew dhcp lease button. if still nothing you might reset the modem (usually hold the reset button until lights flash) then check again
on the other hand if your isp has the modem setup in "bridged mode" there may be no ip to access, then your stuck trying to use the macs pppoe client to connect to the isp thru the virtual pipe thats supposed to be there.
imac g5   Mac OS X (10.4.3)   1.8 17"