iCal sync issues, iPhone 4s & iMac running 10.6.8

I am having trouble syncing my iCal calendars with my iPhone 4s.

I have conflicting information on the phone's calendar and cannot seem to resolve the conflicts without manually deleting them from the phone. The conflicts consist of old events that have changed. Upon sync, rather than changing, the original event remains and a new version appears along side.

When I try to overwrite the info on the phone with what's on the imac it doesn't happen and the sync takes a long time (in excess of 15 minutes). I have done a hard reset on the phone (hold power button and menu buton @ same time until apple appears), no change.

Another goofy thing that happened which may or may not be related is that some custom ring tones i have do not ring through as they used to, the ringtone shows up in the contact, but when they call me I get my defaut ring.

Any suggestions?