The changing of the resolve.conf file by ppp (using usepeerdns) is probably good for the average setup... When the system is runing named as a primary server, it is dumb..... You should check first...
Parse named config files in our ifup-post shell script? I don't think so... You can set PEERDNS=no in your /etc/sysconfig/network-scripts/ifcfg-ppp* files, as documented in /usr/doc/initscripts-*/sysconfig.txt and that will solve the problem for you.