I believe Firefox generally uses the operating system's TCP/IP stack to handle DNS resolution. Does the native browser work correctly on the same machine?

When returning server not found, does Firefox show an altered host name, for example, with www. before and .com after?

Are you using a proxy?

Apple's Safari is still a little too "buggy" for my taste. I haven't tried it.

With regard to changing the host name in the location bar, it depends on the structure of the simple host name.

If the simple host name contains a hyphen, e.g. MNBM01-USD01; the host name will not be modified in the location bar.

If the simple host name doesn't contain a hyphen, e.g. SOURCE; the host name will be modified and appear as WWW.SOURCE.COM.

The search list defined in /etc/resolv.conf has as its last element, GD-AIS.COM. There are CNAME records for both MNBM01-USD01 and SOURCE in the GD-AIS.COM zone file.

I believe this name resolution bug was introduced in one of the Firefox 10 releases.

I tend to use fully-qualified host names when accessing web sites. Occasionally, I will click on URL with a simple host name that someone passes to be in a message to understand the problem they are reporting.

Typically, my stock response is: "We have a distributed network environment with 50 sites, you need to use a fully-qualified host name to ensure that the content can be accessed from another site."

No. I do have a local Squid Web Proxy that I could use. I configured it and know that it would access the correct web site were I to use it.