I had the same problem a while back (with 1.3.71 i think).
The problem went away when I powered down my machine and
recompiled the kernel. It must have been a strange memory
fluke. I had recompiled and rebooted the machine numerous
times to no avail. Powering down the system was the only
thing that fixed it.
I can tell you that PPP does work with 1.3.75. This is
probably a gcc and/or RAM problem.
Rob
(rriggs@tesser.com)