I have several customers who cannot access any subdomains, but the main domains load properly. However, this is not a universal problem. It seems to affect mostly RoadRunner customers, but there are some non-RR people who are also affected. Any suggestions at things I can look at?
Edit: The people affected by this can get to subdomains for some domains on the server, but have difficulty with certain domains.
Found the problem. It was a poor configuration on my part. Lack of entries for the ns1 and ns2 nameservers for the domain hosting the DNS, and a flawed SOA implementation.
Most DNS lookups worked fine because the servers were configured with lax settings. Those that required better verification failed lookups on all subdomains, and some base domains.