Just because both sites are hosted by the same firm doesn't mean they are on the same physical server. Your problem connecting could be attributable to many things.
- User name and password may have changed or been reset.
- Server permissions problems (GoDaddy is notorious for this).
- IP blocking.
- Server is down.
- etc...
Are you able to connect with a 3rd party FTP client like FileZilla? If not, I'm guessing this is a server problem & you need to contact your host.
Nancy O.