I don't know the reason for that problem but by looking at the source code for each link I see they are different.
Is one of the versions of the site forwarded to some freespace? Eagle?
The site could be losing itself in frames, but I can't see this in the source code.
Also according to a domain name search engine there seems to be a problem with the name.
I looked to see where it was hosted and found this:
The IP address from which you have visited the Network Solutions Registrar WHOIS
database is contained within a list of IP addresses that may have failed
to abide by Network Solutions' WHOIS policy. Failure to abide by this policy can
adversely impact our systems and servers, preventing the processing of
other WHOIS requests.
Ask them (NSR) what this means. It could be that the reason for your friends inability to see their domain name in France is a problem with access to another country's servers.
Clutching at straws here I'm afraid.