FTP on SBS2003 R2/IIS V6.0/ISA Server 2004

I've read so many posts on this you would think I could get this solved
but...

I have read http://support.microsoft.com/?id=555018 so many times that
I think I have it memorized. This is the first FTP site that I've
tried setting up so take it easy on me.

I have created E:\FTP and have set it up as an FTP site with isolated
users. I've created \domainname\user subdirectories for 4 customers.
I have created an FTP user security group that has read/write access to
these subdirectories (NTFS permissions). I have read and write checked
in the FTP properties home directory tab.

I can connect using windows explorer using any of the customer logins
and it takes me to the proper subdirectory. I can download a file from
the site but I cannot upload or delete from the site. I can do this
from a computer on the intranet or a computer on the internet (both get
identical results).

From IE I get Details: 200 Type set to I. 227 Entering Passive Mode
(192,168,0,210,88,19). 550 Access Denied.

From command prompt using FTP I get: 200 PORT command successful. 550
Access Denied.

I believe that I have all the permissions setup properly as well as the
firewall/router settings but evidently not. Any help in pointing me to
the right direction would be appreciated.

Thanks in advance!!

Roger

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