I had the same problem as everyone else with the conflict error described above on both my iphone 4 & my ipad 1. I solved my problem eventually by doing a couple of things of which I list below:-
1. I went into itunes Edit, Preferences, Devices, and deleted all of my backups so there wasnt any backups for any device. For the sake of it I also reset my sync history.
2. I then clicked onto my iphone on LHS & onto the Info tab at top. I changed my 'Do not sync events older than XX days' setting. I originally had 45 days and changed it to 30 days (I changed my ipad to 7 days when I synced that),
3. I scrolled down to the Advanced section and ticked the 'Contacts', 'Calendar', 'Mail Accounts', 'Notes' boxes for this time only, and re-synced both my iphone & ipad separately. The problem disappeared for both devices.
It is also worth pointing out that on both devices, I used to have more than one calendar in operation (since the launch of OS 5.0 & icloud etc), which I feel caused the problem in the first place? Consequently, I only have only one calendar now in operation (synched from MS Outlook on my PC). In other words I don't use icloud anymore and switched it all off in both devices. I only sync with my desktop PC & with the cable again. I would rather sync this way and be free of this damm problem than syncing with icloud & getting the problem back again.
I hope this helps all the frustrated people out there. Good luck.