It can't be my DSL router or my ISP blocking a port.  I am mining just fine with mtred.com and 50btc.com.

This is only Deepbit I am having a problem with. 

Same problem in 3 different farms on 3 different internet connections in 3 different locations.

Cannot resolve pit.deepbit.net.  It comes and goes.  Sometimes I can resolve it, sometimes not.  Sometimes it works for a day, sometimes an hour.   I have been mining fine for over a year with the same settings.  This all just started happening after the last Deepbit DOS. I have tried different DNS servers. 4.2.2.1, 4.2.2.2, 8.8.8.8, etc.

Is pit.deepbit.net changing it's IP address frequently maybe to combat DOS?  Is there a better DNS server to use? 

Thanks