How do I get rid of multiple calendar events on my iPhone?

iPhone calendar is showing multiple instances of the same event for most of my iCal calendars. I am not using iCloud, although I tried to a while ago and the problem began then. The problem stopped but has returned. I have signed out of iCloud, exported all calendars, trashed the contens of User/Library/Calendars and re-imported the calendars. I have done this many times in fact and still have the same result. Some events repeats as many as 15 times on a single day. I am using OS 10.7.5 with iCal 5.0.3. The phone has IOS 5.1.1. Thanks in advance for any help with this.