The problems aren't with MacTCP, the problems are with Samba. For example, from http://home24.inet.tele.dk/ccadams/se/samba.html ...

"Do not close any windows as this crashes the Mac; also quitting MacWWW seems to cause a crash. Note that with System 6, MacTCP may crash when saving prefs for the first time, so check that the prefs are actually saved".