I also have this same problem with my evolutionx dashboard. I have an X3 bios installed and I am able to FTP files to my xbox with no problems by just leaving my xbox in the bios screen. I also can transfer files via FTP whenever XBMC is running. So technically the fact that I couldn't upload files all that well while evolutionx is running was a non issue since I can upload files with either my X3 bios account or my XBMC account.
But it would still be nice to know why i'm getting the same error as the above user.
I'm using flashFXP and initially I had tried going into options under the evolutionX account on flashFXP and checking the box next to "Use Passive Mode"
I tried that and got this msg
[R] Connected to evolutionX
[R] 220 Please enter your login name now.
[R] USER xbox
[R] 331 Password required for xbox.
[R] PASS (hidden)
[R] 230 User xbox logged in , proceed.
[R] SYST
[R] 215 UNIX Type: L8
[R] FEAT
[R] 502 feat is not implemented.
[R] REST 100
[R] 502 rest is not implemented.
[R] This site may not allow file resuming
[R] PWD
[R] 257 "/" is current directory
so i'm not sure if i'm heading in the right direction or not