DNS http://domain & www. errors

[fraggle]

I am getting intermittent problems with all domains on one box running on apache and i suspect problems with config.

Problem:
Websites only visible at [domain.com...] and not www.domain.com intemittently.

So far looked at wildcard DNS record or my Serverand it set for a ServerAlias entry (set to *.domain.com)

Any otherproblems it could be as it is still occuring