This might be a clue with AmiTCP, it can use multiuser, but since PFS3 install only uses the multiuser.library. AmiTCP could be detecting this library presence and thats why everything bar AmiTCP is working?
Found this on
http://www.faqs.org/faqs/amiga/AmiTCP-faq/
7.6: Do I need MultiUser?
No. However, MultiUser is very handy if you plan to have your machine on
the net all the time. Unfortunately, MultiUser and AmiTCP don't use the
same format for the password file.
There is a replacement for usergroup.library that uses the MultiUser
password file. It may be found on in the util/libs directorory on Aminet.
<ftp://aminet/util/libs/MuFS_UserGroup.lha>
MultiUser is on Aminet.
So how to force amitcp not to try to use multiuser.library if my idea is correct.