If your security programs and Windows Firewall are disabled, open Network and Internet from the Control Panel and then double-click Internet Options. Press the Security tab and move one by one the security level scroll bar for Trusted Sites, Local intranet and Internet to Low:

After that, select Trusted sites, click Sites, and type http://www.larousse.fr
in the first field. Press Add and then close the window. Next, click the Connections tab, press LAN Settings button and make sure that box below Proxy server is not checked. If you still have issues, I suggest you contact the developers. Their email address is conso@larousse.fr
.