Fixing DNS is a tricky thing, with cpanel there is a couple steps to try first.
DNS failed you are not sure why, try this first:
Still not working, try this:
Basically DNS has about 5 files that need to all be in sync for named DNS to run.
I highly recommend running three servers with DNS so you have back ups if one servers fails. In this case you just transfer over the dns files and restart. Here is a list of the DNS files that need to be transferred.