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:

/scripts/cleandns
/scripts/rebuildnamedconf

Still not working, try this:

/scripts/rebuilddnsconfig
/scripts/fixdns

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.

named.conf.cache

named.conf.zonedir.cache

named.conf

named.conf,v

named.conf_back

named.conf.fixrndc

named.conf.prefixrndc

named.conf.rpmsave