VSFTP with 2 IP adresses

[mephivio]

Hi,

i'm under ubuntu 12.x
My VPS has two ip addresses: for examples : 5.1.1.1 and 5.1.1.2

Web sites hosted using address 5.1.1.1 (my default address) are well served by vsftp
i can use filezilla (with sftp settings) and all works fine

web sites using address 5.1.1.2 can't use sftp (it doesn't work) and i can connect only with active profile (passive doesn't work)
i can't tarnsfer php or css files (it blocks every time). if i cancel teh tarnsfer from filezilla i see is present on the server.

I use CSF (but i disable it to be sure it doesn't interfere)...

Any idea ?
thx