I had the same problem here when they put in my dsl.  Problem is you're
getting double network address translation.  I'd hae to look up my modem
model, but I have some files that tell what to do.  If you're running a
router as I was, call tech support or I can send you the files if the
modem is the same, and tell them you want the modem set up as a bridge
only.  You then set up your router to do the login and so forth.  You can
then look at the status link on your router and see what your i p address
is.
73s
Butch Bussen
wa0vjr