It's definitely the call to uploadPhotoAsData that kills it, not the actual publishing of the stream or any of the little things I do during the process, I've been able to narrow it down pretty conclusively to that.
I just don't really understand the code in the FacebookAgent.m file well enough to fix it (he's a better programmer than me, that's for sure).
Code:
[fbAgent uploadPhotoAsData:myData withCaption:nil toAlbum:nil];
Also, even if I use the nifty sample project that AmanApps posted (Facebook Agent Test) it crashes in exactly the same way if I use uploadPhotoAtURL or uploadPhotoAsData. Anyone else see a bug in there that we can fix? I know there are others with variations on this same problem. Maybe I just don't understand the NSDictionary ---> NSMutableDictionary fix that was mentioned....?