iCal sync to iPhone repeats all moved events

I'm struggling with my Calendars, I think since updating my iOS on the iPhone 4 to 7.0.4.

Usually there's no problem syncing iCal (version 4.0.4) to either the native iPhone Calendar, or Week Cal app, but recently I'm getting duplicate events on the iPhone where I've moved them in iCal.

I'm getting the event in both the old position, and the new one, leading to chaotic duplications every time I move anything in iCal. The iCal calendar on my MacBook Pro stays clean, but the iPhone version is a mess.

I've tried deleting all the calendar information, and then turning the phone on and off to reset it, then re-syncing the Calendar info. from the MacBook, but the same thing keeps happening.

Can anyone help with a diagnosis, and hopefully a cure... ? My calendar is essential on my phone and is currently un-useable.

Thanks