We've got a website (hosted locally but available over the internet) that does not work for everybody. The problem has been reported by internal users having windows vista home. If they go on our website with this address http://example.com (the bare domain), everything is fine. If the address is http://www.example.com (with the www subdomain) it doesn't work, they get a simple error message that suggest to reload the page. It's not all Vista users that have this problem.
For the rest of our group, both address are working. Our server (Windows Server 2008) accept both headers. Cache has been cleared and all browser get the same error on those vista home, so I don't know what to do more. Any ideas?