I suppose your password has some special characters in it.
Please read:
https://winscp.net/eng/docs/session_url

I am trying to upload files to sftp site.
when I use open username@host.com:port and type in password when asked I can log in successfully.
but when I use a script I get denied error.

2012-04-12 13:22:05.418 Looking up host "host.com"
. 2012-04-12 13:22:05.418 Connecting to ip port
. 2012-04-12 13:22:05.512 Server version: SSH-2.0-Connect:Enterprise_UNIX_2.4.04 Build 00
. 2012-04-12 13:22:05.512 Using SSH protocol version 2
. 2012-04-12 13:22:05.512 We claim version: SSH-2.0-WinSCP_release_4.2.2
. 2012-04-12 13:22:05.559 Doing Diffie-Hellman group exchange
. 2012-04-12 13:22:05.684 Doing Diffie-Hellman key exchange with hash SHA-1
. 2012-04-12 13:22:06.153 Host key fingerprint is:
. 2012-04-12 13:22:06.153 ssh-dss xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
. 2012-04-12 13:22:06.153 Initialised AES-256 CBC client->server encryption
. 2012-04-12 13:22:06.153 Initialised HMAC-SHA1 client->server MAC algorithm
. 2012-04-12 13:22:06.153 Initialised AES-256 CBC server->client encryption
. 2012-04-12 13:22:06.153 Initialised HMAC-SHA1 server->client MAC algorithm
! 2012-04-12 13:22:06.278 Using username "1234".
. 2012-04-12 13:22:06.372 Keyboard-interactive authentication refused
. 2012-04-12 13:22:06.372 Prompt (6, SSH password, , &Password: )
. 2012-04-12 13:22:06.372 Using stored password.
. 2012-04-12 13:22:06.372 Sent password
! 2012-04-12 13:22:06.418 Access denied
. 2012-04-12 13:22:06.418 Access denied
. 2012-04-12 13:22:06.418 Prompt (6, SSH password, , &Password: )
. 2012-04-12 13:22:06.418 Disconnected: Unable to authenticate

My script has the following
open user:password@example.com:port

Also I am able to post the file through the interface.

Any help will be appreciated.
Thanks!!!