Besides the normal networking Problems
Some ISP's Do Not Allow Some Servers To Run, And Or Block Some Ports Some Servers Run On. This Is Normally Not An Issue (And May Not Be In This Case), But There Have Been Reports From Some Users That Some Providers (Mine Included) That Block Some Ports.
Now "NetZero high speed dial" up Is Nothing But A Farce Where They Strip Out Data Making The User Feel Surfing Is faster. Including Data Compression, Striping Out Data From Images (Making Them Look Not As Good), And Scanning Ahead (Downloading Data When The Modem Is Idle).
I Have Never Heard Of A Dialup (high speed phone). Dialup Modems Are They Not Limited To 56k (Normally Lower)?
DSL Modems Are Not Dialup So I Am Not Sure What A High Speed Dialup Is.
because the DSL provider uses NAT to assign "fake" IP addresses to their customers.
Yes that can be a major problem.
Some Dialup ISP's also will Lease A IP address to the user for a matter of Min's or a few hours. AOL was good for this once (maybe still) so once you do get it working the IP Address lease will expire and the ISP will assign a new IP address and the connection will be broken.