Is Xfinity blocking my DNS responses?

For some reason, when my computer is connected to the internet via my Xfinity home WiFi connection, and using the DNS configuration that was automatically configured, I cannot do any DNS lookups for my domain, (foxcove.com).

On other networks, the same DNS lookup ("dig foxcove.com") returns the expected information.

I did recently (a few hours ago now) find that a site called spfbl.com had he domain on a blacklist, but I followed the procedure for clearing that, and they say it was successfully removed from their list. I was hoping that might do the trick, but the Xfinity DNS servers still won't return DNS records for the domain.

Things were working OK until a few days ago.

Can somebody shed any light on what might be going on?

Thanks,

  - Richard