can not upload file

Hi, everyone
I installed the latest version SmartFTP. my OS is WIN 2000 Pro. I could down load file from remote sever, but I couldn't upload my local file to remote sever. the transfer is setup to passive, everysettings are default.
the msg is "no data connection". could anybody help me to solve this problem?
Thanks.

may

Can you post a detailed log? also, you have a router, software firewall, etc?