I couldn’t connect through FTP while trying to access some of my domains and I didn’t know that the culprit was Norton Antivirus even after brainteasing a couple of days. Suddenly it flashed me that it might be something because of firewall/antivirus and when I turned off Norton’s Worm Protection, I could connect. So I thought it would be better sharing it here that someone on the internet might benefit from it.

Here’s the fix:

Open Norton AntiVirus
Click “Options”
Click “Internet Worm Protection”
Make sure “Enable Internet Worm Protection (recommended)” is checked.
Click “Trojan Rules”
Uncheck “Unused Windows Services Block,” (all the way at the bottom of the list)
“OK”
“OK”
Connect to your FTP site using your FTP client (It’ll work.)

Go back to Norton
Click “Options”
Click “Internet Worm Protection”
Click “Program Control”
You should see a new entry, “Microsoft Application Layer Gateway Service.”
It should be configured as “Automatic.”

This is what fixed the problem. (You don’t have to make any changes here; this step was just to let you see the new entry.)
“OK”
Click “Trojan Rules”
Put the checkmark back into “Unused Windows Services Block”
“OK”
“OK”
Close Norton
You should now be able to connect to your FTP site.

One More Thing: If you have Windows XP Pro Service Pack 2 installed, you may at some point have to tell Windows Firewall to not block your FTP client software. To do so,

Open the Windows Control Panel
Click “Windows Firewall”
Click the “Exceptions” tab
Click “Add Programs”
Check “Your_FTP_Client_Software_Name”
The Scope should be set to “Any computer (including those on the Internet).”

Hope this tip has solved your problem. Happy using FTP.