After migrating from MobileMe to iCloud, I ran into a nasty situation where iSync/MobileMe sync thought I had data conflicts but I couldn’t resolve them.
The way the Conflict Resolver dialog appears and acts is a nightmare. When it appears, it hangs for a good 30 seconds, spiking the CPU and not allowing itself to be clicked on or dismissed. Then when you do tell it to go away (Resolve Later), it pops up again in the same infuriating state a few minutes later.
With the conflicts failing to resolve and this appearing every few minutes, my machine was completely unusable.
The solution to this (according to my experience and everything I found in my web searches) is to go into MobileMe and reset sync data. Pretty simple, except that feature is no longer available once you migrate to iCloud.
I tried rebooting, etc. to no avail.
Ultimately I dug into my Library/Preferences folder and looked for anything with ‘sync’ in the name. I could see in Activity Monitor that there was an iCalExternalSync process (I didn’t write down the name, it was close to that if not exact) working hard, so I manually trashed the following files:
That did the trick.
Hopefully of use to the next person who runs into this issue.