guess what, i changed the following:

FTPD="/home/backup/incremental"

to

FTPD="incremental"

and now it works! but not sure if called from cron job will it be oky need to check again.

Based on the above i assume that ncftp logins the user "backup" and using fullpath it failed to create "incremental" dir into its own dir?
or am i doing something wrong with the config?