OK, many years ago I started playing with ftp mainly to connect to my Dbox2 to re flash it, as well as running my own web server and connecting with ssh and ftp. So I know there can be some issues with setting up ftp.
So now I only ever do it this way,and it works 100% every time.
PS3 Network setting
Def/Router: 10.10.10.11 < same as ps3's IP
Prim/DNS : 10.10.10.1
Network speed stays at auto
MTU 1400 < but can be left to auto,
no proxy server
Now I'm using a laptop to do all my FTP'ing to the PS3 using a cat5 crossover cable, as my ps3 is not on my home network, but if I need the ps3 to be, I just jump it on to the wireless router. Anyway I stay connected to the wan/lan on the laptop using the lappy's wireless, so I still have Internet if needed. Now I change my settings on the built in net card to This.
Lappy network settings.
Def/gateway 10.10.10.11 < same as PS3
I set my FTP prog to only allow 1 simultaneous connection and it fly's back and forth like no tomorrow with files, very fast indeed. anyway this is my way and works well for me, because I'm not going though a router slowing things down, i don't use a firewall on this connection and its also safe hidden away from Sony eyes when I'm copying installing and looking around their file structure, unlike when connected to the Lan.