I just set up my first Windows 2003 IIS 6 server and after a bumpy start (I've only ever managed a Linux server) I had just about everything set up. Trouble is, I've been having a heck of a time uploading files to the server via FTP. For some reason, files over 1mb will sometimes toss back an error -132 once the progress hit 99%. Oddly the file transfer actually completes despite the fact that the client receives the error.
Messing around with the built-in Windows firewall settings didn't help much nor did changing clients. The only thing that worked was turning off the firewall completely. Figuring the problem was likely a flakey IIS FTP, I downloaded a 30 day demo of Gene6 FTP and tried that since it integrates with Plesk.
Installation was a breeze and I had everything running in minutes, it even ported all my accounts over (since it uses the Windows accounts by default). Trouble is it didn't fix my problem, in fact now it's worse. With Windows Firewall enabled *no* upstream transfers over 1mb will complete using Gene6 compared to the sporadic behavior of IIS. I've added exceptions for ports 21 and 20 and added in a range of passive ports but it didn't help. I even added the g6ftpserver.exe app to my exceptions list but that didn't help either. As with the built in FTP server, turning off Windows Firewall on the server is the only thing that solves all my problems.
You actually don't need to buy a firewall for Windows 2003. There's a MMC that you can install called "Routing and Remote Access". RRaS is a much more advanced firewall then Windows Firewall and it can do more then just act as a firewall as well.