So I was trying to switch adamdoupe.com over to posterous (an amazing service).
Adamdoupe.com is registered via GoDaddy, and posterous even has a help
section on how to switch DNS. However, the Total DNS setting was
disabled in my account, and I figured I would post my problem/solution
here so I can help out anyone else with this problem.
 
The problem was that I had Custom Nameservers enabled. With this you
can't enable TotalDNS. The solution is simple, switch from Custom
Nameservers to Parked Nameservers. Then you can enable Total DNS
to have your domain point where ever your little heart desires.