DNS port blocked?

I've stopped receiving traffic on UDP port 53, which is a problem since it means my DNS (and therefore mail) are pretty much dead in the water.  Things were fine several days back, and nothing has changed on my modem or LAN settings.

Comcast opened a support incident, but the most recent call I got with an 'answer' was a voicemail, and displayed a complete lack of understanding of a) my account & network configuration, b) the capabilities of the modems Comcast gives customers, and c) basic networking.  

Of course there was no was to call back to continue the conversation... and they closed the incident witout verifying, well, anything.  Everything he said was prefaced by 'they said that', which indicates that there *are* people at Comcast who understand more about networking.  I suspect that the problem statement got garbled between me and those folks.

Is there a way to get in touch with someone at Comcast that can address problems more directly?  Every time I've called I've ended up starting over with tier-1 support.  This is *not* what I expect from business class service...