There are currently 236 Freepers on the list. I have no problems with any other postings.... just the Ping list. It only happens when I am posting the list. Is there perhaps a limit in FreeRepublic on the number of addressees?
To get into specifics of your problem you need to communicate with John Robinson. He designed and maintains the software. The mods have no special knowledge of it.
The GGG main list has 588 names, and no duplicate post problem. Of course, I *am* running OS 9.2.2, and you're running X... ;') What happens with the GGG list sometimes is that, after it gets done, nothing comes back (blank screen, with "Posting Comment" still in the title tab).