When Sync History was reset was it done via iSync or Terminal? Apple says if problems persist after resetting via iSync then do it in Terminal. See doc
http://docs.info.apple.com/article.html?artnum=306484
One thing I forgot to mention is I had turned off .Mac synchronization before resetting Sync History and checking "Publish Blocked Actions". I turned it back on after successfully syncing with iCal. I vaguely remember something about .Mac interfering with resetting sync history.