Ftp server and dial up

Hi

I always struggle to get the following right. I installed a ftp server(MS
IIS) on a xp pro service pack 2 machine (Machine A).

I can access the ftp site from another pc (Machine B) on the same network
using a crossover cable. If I dial into the Machine A using a dial-up
connection from machine B, I can't get the ftp to work. Has it got
someting to do with my ip addresses or what. If I look at the dial up
connection properties whn connected, I can see that the IP addresses changes
everytime. Is this problem?

Thanks