> Everytime I try and run pppd, I get the following messages:
>
> The remote system is required to authenticate itself but I
> couldn't find any secret (password) which would let it use
> an IP address.
> 
> Does anyone have ANY idea what might be the problem?

i had this problem while testing a modem in that 486 machine i
posted about a few days ago.  the 486 was set up to run dhcpcd
on boot to obtain an IP address from my main box.  without
shutting down the DHCP-configured eth0 interface, i decided to
try the modem in the old box, just to see if it worked.  but
since the system already had a default route (through the main
box), pppd gave me the error above.  so i added the 'noauth'
option to the pppd command line, and everything worked fine.
you could also add 'noauth' to the options file specified by
the 'call' option.  see pppd(8) for details.

taken from the 'Frequently Used Options' section of the pppd(8)
man page:

auth

Require the peer to authenticate itself before allowing network
packets to be sent or received.  This option is the default if the
system has a default route.  If neither this option nor the noauth
option is specified, pppd will only allow the peer to use IP
addresses to which the system does not already have a route.

noauth

Do not require the peer to authenticate itself.  This option is
privileged.

hope this helps,
matt lee