I am having the same problems.

I am frustrated and probably don't know what I'm doing. I have a test
server up and all my PC clients can reach it fine. My Mac clients
cannot. Everyone
is on the same subnet here. I can ping the server by name, by FQDN,
and by IP from The Mac but not via HTTP. The error is 'server not
found'.

I have tried various authentican schemes, and I have anonymous access
activated, and added to the guests group and even gave it 'everyone'
permissions - thinking maybe it was an authentication problem.

My goal is to have a public facing site  that supports Mac and PC that
also has links to secured portions or sites. I want no login required
coming to the site, just when you try to access secured areas.

Any Free clues?

Check Alternate Access Mappings in Central Admin, Operations. Verify the
URL being browsed to from the Macs is specified.

Next, verify the Host header is specified on each WFE server rendering
Web App content. From IIS manager, virtual server properties, home
directory, advanced tab. Every URL should be specified *exactly* as it
is typed into the browser  address bar. So, if users type http://portal,
the host header should be portal. If it is http://portal.mycompany.com,
then portal.mycompany.com is the host header. This must *exactly* match
the Alternate Access Mapping as well.