If you're able to login, then the passwords and configs are probably set correctly. It would be either:
1) a permission issue, either with the wrong ownership on the files and directories ..
or
2) a wrong UID/GID value in the /etc/proftpd.passwd file.
So do a mass chown on your public_html, eg:
Code:
cd /home/[B]username[/B]/domains/[B]domain.com[/B]
chown [B]username:username[/B] public_html
If that doesn't work, figure out your uid/gid:
id username
then check the /etc/proftpd.passwd for those number (3rd and 4th colon separated columns) and make sure they're correct. They should be the same numbers as the system account.
Failing everything else, shut down proftpd, type:
proftpd -n -d 20
to load it up in debug mode and see if you can spot the reason there.