Can't Access Sub FTP Account Using Explorer

I have a few domains that I recently migrated to cPanel.

I created a 2 ftp accounts on one domain and (example bill@site.com and john@site.com), both accounts can be accesed using ftp clients, and also from Opera browser with this info:

ftp://site.com:21/ or ftp://server-ip:21/ - username bill@site.com or john@site.com and passwords.

But, this accounts can not be accessed using Internet Explorer, and my customer only uses IE , the error I recieve is something like this:

Code:
FTP Directory Error

Windows does not have access to that folder. Make sure the name of the directory was written ok and you have permission to access that directory.

Details:
The connection with the server was reset
I already tried restarting pure-ftpd, flushing the firewall rules, and there problem stills..

Im using RHES 4 + lastest kernel 2.6 and the latest release version.