FXP问题请教

在两个盒子之间般数据，肯定是fxp方式最简单，传输碰到了如下错误，请教大神解答原因

[左] TYPE I
[左] 200 Switching to Binary mode.
[左] SIZE .rtorrent.rc
[左] 213 817
[左] MDTM .rtorrent.rc
[左] 213 20120518140903
[右] TYPE I
[右] 200 Switching to Binary mode.
[右] SIZE .rtorrent.rc
[右] 550 Could not get file size.
[左] PASV
[左] 227 Entering Passive Mode (94,83,14,115,195,80).
[右] PORT 94,83,14,115,195,80
[右] 200 PORT command successful. Consider using PASV.
[右] STOR .rtorrent.rc
[右] 500 OOPS: vsf_sysutil_bind
[右] 500 OOPS: 500 OOPS: child died
[右] 传输失败!

部分vsftpd.conf配置文件:
download_enable=YESpasv_enable=YESport_enable=YESpasv_promiscuous=YESport_promiscuous=YESpasv_min_port=50000pasv_max_port=50020write_enable=YES
补充一下，ubuntu环境，没有selinux.