HTTP SERVER: Sending prolog query...ERROR: Http error: 407

I have the message "HTTP SERVER: Sending prolog query...ERROR: Http error: 407" trying to connect to OCS. Que dois-je faire (what may i do ?) IE is correctly configured, i'm able to ping the server and the server respond to an another machine.

Here is the message in the log file ! Thanks for tour advises (merci pour vos conseils).

HTTP SERVER: Creating CInternetSession to get inventory parameters...OK.
HTTP SERVER: Getting HTTP Connection to server monserveurocs port 80 using no authentication...OK.
HTTP SERVER: Sending prolog query...ERROR: Http error: 407
Failed because Unknown exception !
Exiting...