FTP Fail - 530 error (not server)

using 10.6.8 in an iMac

i can't log in to use FTP - fails with 530 login auth failed.

I was able to use ftp earlier today, but then it stopped working. Here's the story so far:

1. Using Dreamweaver - Tells me Password or Username is incorrect.
2. Re-enter details 50 times. Double check them, re-enter details. Still the same error.
3. Tried another site (hosted on another server with their own username and pass) and a couple more. Still the same error.
4. Installed Filezilla, tried to connect to ftp using the details i know are correct and get the 530 login authentication failed error.
5. Tried another site, same problem.
6. Checked on another computer on the same network - same OS, MacBook. Connects perfectly every time.
7. Tried the original machine, but this time used a different wifi connection (teathered from my phone) - same problem.

8. Opened terminal and did: ftp mysite.com [enter] myusername [enter]

331 User myusername OK. Password required

Password:

530 Login authentication failed

ftp: Login failed

9. Tried using filezilla's network config utility.. if i just click next>next>next>test i get:

Checking for correct external IP address

IP 10.0.0.7 ba-a-a-h

Response: 510 Mismatch. Your IP is 71.197.235.250, hb-bjh-cdf-cfa

Wrong external IP address

But it can't be the router, because the other computer worked - right?

So what's going on & what can i do?

Thanks for any help you can offer!