connecting to internet

[cagold]

Recently when I try to connect to the internet I get the
following message right after contact is made with the ISP.

All devices connected.
Error 50: The request cannot be supported.

I've never seen this before and can't find anyone
else who has.

Windows XP; Prodigy;

A computer sitting next to this one connects fine with (I
think) the same settings. The two computers used to be
networked, but not now.

Help please.
cagold