having the same problem. the smf package administrator is bugged i think. here is your info, if you still need it:
let's say you have the subdomain
http://test.vndv.com/FTP server: test.vndv.com
username: test
password: your signup password
path: /www/vndv.com/t/e/s/test/htdocs/[path to smf]
path to smf usually is either SMF or FORUM (depends in which folder you copied the forum files)
and if you didn't get how the path is generated it's like this:
/www/[server_name_without_www]/first_letter/second_letter/third_letter/domain/htdocs
(first, second and third letter are the first 3 letters of your subdomain name)
hope it helped but even with the correct settings i can't get TP to install