I use a LOT of recurring events (I'm a psychiatrist). The iPhone iCal software does not handle the deletion or change of a single repeating event. This renders my iPhone iCal application unusable because it is never accurate. I have to refer to the google calendar for accurate reference on the iPhone but cannot use it to make changes to my schedule. (My google calendar and iCal are synced in both directions). Resetting sync history, turning calendars off and on, etc is not going to fix the underlying problem since it will simply recur the next time a repeating event is modified. The workaround is to manually change each and every event on the iPhone. Forgive my sarcasm, but that is like walking everywhere as a workaround for a flat tire - hardly qualifies as a fix!