Use MacTCP Watcher to check that MacTCP is working properly.
Try reinstalling MacTCP - delete MacTCP, MacTCP DNR, and MacTCP Prep from the System Folder, Preferences, Control Panels, and Extensions (watch for duplicates), then reinstall from the original disks.
If the login takes a long time, ensure that you have not enabled Far Servers or Server privs in FTPd Setup.
Try disabling all non-essential inits (ie, everything except MacTCP and other network related inits). Try toggling VM or 32-bit mode.
If FTPd crashes (ie System Bomb), try installing Macsbug (available from ftp.apple.com:/dts/mac/tools), when it crashes in to Macsbug, type:
log yourharddisk:logfile
sc6
sc7
td
how
hc
ht
il pc-10
dm sp 100
dm a6 100
log
es
and send me the log file.
Please try to ensure that the bug is repeatable - if it happens once, its a glitch not a bug, and its unlikely I'll be able to do anything about it.
Please DON'T say anything like "I'll pay the shareware fee if you fix this". This applies to feature requests as well, DON'T say "I'd pay, but I can't use it without feature X". If you find a bug or want a feature, tell me about it. If you use FTPd, you have to pay for it. The two are independent of each other.