Can you log into your modem?
You also may want to try knoppix. Its a live linux CD that does some amazeing automatic hardware detection. It doesn't touch the hard drive (unless you tell it to), but runs soley in memory. You may find it to be a different perspective. I know that you aren't on the net personally, but you could download it from where ever you're posting from, or ask a friend to.
(check out the configuration button in the lower left corner, next to the K menu)
Again, if it is possible to log into your modem, then I say the odds are strong that the problem is there.