Isn't this a variation on the "webserver user id's are denied access to networked resources" problem?

The fix is to change the account under which the service runs from the default to one that you give the rights required to access network shares. This is done through Start->admin tools->computer management->Services & applications->Services. Bring up the Properties dialog on the apache service, select the log on tab and fill in details for the userid/password to use. Stop/start the service.