Does the url need to be in quotes maybe? Or (depending on the nature of your download) the site requires a referrer equal to the address or hostname of the site itself, so they know you're not getting their torrent linked from someone else's site. Either way I usually use a script to do this after downloading the file:
btdownloadcurses --max_uploads 15 "$1"
That way you can just save it in your path as btget or something and just invoke it by typing "btget the.torrent". Another plus to this is that if you're interrupted (i.e. you have to restart or the power goes out or something) youc an just restart the torrent without even opening a webbrowser window.
Don't forget to run btdownloadcurses with NO commandline parameters to see what options you can invoke in the script: --max_upload_rate, --display_interval, --min_peers, --report_hash_failures, and more.