bobmitchell wrote:...but is the first time I have tried building compilations from numerous CD's.
It wouldn't surprise me if that is the source of the problem and that Nero has a bug that prevents it from properly handling more than a few distinct source CD's. You might want to make sure that you have enabled the "Cache the track on harddisk before burning" option on the CDA options of the new audio complilation dialog and also check the cache settings in File->Preferences to make sure you have enough room to cache all the ripped tracks.
If that doesn't clear it up, I would suggest not messing any further with Nero for the ripping part and instead use CDEx, EAC, Feurio, etc. to rip the tracks to your hard drive in .wav format. Then after you have ripped all the tracks, burn the compilation directly from those ripped tracks on the hard drive. Yes, it is a little less convenient because it is a two-step process, but it is probably less hassle than trying to figure out a potential bug in Nero.