Ive never set the nameservers to that of the parked site. Rather I just enable forwarding, and enter the URL to forward to. Works for me If your still having problems I would suggest giving GOdaddy a call, their support is 24.7 so you should get right through.
The issue is with the '6-24 hours to propagate' for the *redirect*.
I remember a while back when it used to be almost instantaneous.
The resolving to GD nameservers is almost instant - if parking with them (for the redirect) so they conveniently get any PPC from parking - whereas the forward/redirect part takes a bit long conveniently in GD's favor it seems...
Edit: domainer50
I too have just used the forward/redirect option (assuming it auto overrides the previous option 'custom n/s' ) but with the result that it just resolves to a GD parked page with no redirect (almost 24 hrs)
I'll see how it goes and maybe give 'em a call.
Cheers