What is your xbox static IP set to?
I found a topic once with these settings, so I used them and it worked. I don't know if it will help you, but here it is:
IP Address: 192.168.0.2
Subnet Mask: 255.255.255.0
Gateway: 192.168.1.1 (I can't remember why mines set to that, or if it matters, but it aint broke, so...)
DNS 1: 0.0.0.0
DNS 2: 0.0.0.0
IP Address: 192.168.0.1 (do not use 'Obtain Automatically')
Subnet Mask: 255.255.255.0 (should auto fill to these numbers)
Leave the other crap blank.
Also make sure you're ftp'ing with the username xbox and the password xbox and that that user/pass combo is correct (check your xbox network settings)