Alright... this is a weird one. I have a client who can get to his web site: bid-advantage.com, but not www.bid-advantage.com

Here's the DNS setup I have via GoDaddy's Total DNS control:
@ -> A -> linode's ip
www -> CNAME -> @

And for my Apache conf I have:
<VirtualHost *>
ServerName www.bid-advantage.com
ServerAlias bid-advantage.com *.bid-advantage.com and some others
docroot & log configuration...
</VirtualHost>

I can get to both sites just fine (as well as everyone else I've had try this.

Any clues as to where the problem lies?

Weird. I can get to it just fine, so it doesn't look like anything is amiss with the DNS lookup or the Apache configuration. Did you set the reverse DNS on Linode?

If he is the only one who is having problems then it sounds like something that he is doing (or not doing). How is he trying to connect to the web site? Through some ISP or through Linode?

Oops... he can get to www, but not simply the domain name. This is interesting considering I have www setup as the ServerName in Apache and the domain name is simply a ServerAlias.

The site used to be hosted (w/ DNS) on ImHosted (worst host ever!) and the client could not reach the site at all! The client's ISP's DNS servers couldn't resolve the domain at all until one day they magically could. In that case I had no idea if it was the ISP's fault or ImHosted, but it was quite bizarre as well.

I don't have any DNS server setup on my linode, but if that would help, I'm game (GoDaddy's "Total DNS Control" leaves something to be desired.

If you don't feel like setting up DNS on your Linode, I highly recommend ZoneEdit. It works and it's FREE.