ftp transfers timeout with Windows Firewall/ICS activated

This problem is regardless of what ftp-client I use and by browsing the web I
have found out that more people have this problem.

When using a ftp-client to download files from ftp-servers on the internet
the connection timeout when all data is transferred and the ftp-client have
to reconnect to transfer the next file. This does not happens with files
small enough to transfer in a few minutes.

This problem occured after I installed SP1 for Windows Server 2003. If I
disable the Windows Firewall/Internet Connection Sharing Service the
transfers work correctly. I have disabled Windows Firewall on all network
connections but that does not help.
I have two NIC's in the server, one connected to the internet thorough a
ADSL PPPoE connection and one connected to my private network where I want to
use ICS to let other computers access the internet.

As it is right now I have to chose between trouble free ftp transfers on the
server and internet access on the other PC's.

Thankful for any help,
Hans

Still no solution with this problem so I made a workaround.

I installed RRAS+DHCP and disabled ICS and that is working but requires a
little more configuration.