something wrong with socks proxy?

[cynix]

seems i can't connect thru socksonline when the ip is in a big decimal number form...

direct connection, no problem:

Connecting to 1023123123
Connected to 1023123123 Port xxxx
220-Serv-U FTP Server v4.0 for WinSock ready...
USER xxxx
331 User name okay, need password.
PASS (hidden)
230 User logged in, proceed.
SYST
215 UNIX Type: L8
CWD /
250 Directory changed to /
PWD
257 "/" is current directory.
TYPE A
...

but using socksonline, i get this error:

Connecting to 1023123123 via Proxy
Connected to Proxy 127.0.0.1 Port 1080
SOCKS Error: General SOCKS server failure.
Connection failed (Connection lost)

but if i setup a socks proxy on localhost, and specify an external socks proxy in it, it works:

Connecting to 1023123123 via Proxy
Connected to Proxy 127.0.0.1 Port 1080
220-Serv-U FTP Server v4.0 for WinSock ready...
USER xxxx
331 User name okay, need password.
PASS (hidden)
230 User logged in, proceed.
SYST
215 UNIX Type: L8
PWD
...

or if i set socksonline's port to 1081, and use that as an external socks proxy in my local proxy, everything's fine:

Connecting to 1023123123 via Proxy
Connected to Proxy 127.0.0.1 Port 1080
220-Serv-U FTP Server v4.0 for WinSock ready...
USER xxxx
331 User name okay, need password.
PASS (hidden)
230 User logged in, proceed.
SYST
215 UNIX Type: L8
PWD
...

any idea what's wrong?