Mac OS X provides several log files that keep track of system operations--a resource that can be extremely valuable when troubleshooting issues. When Mac users experience problems with MobileMe syncing, the sync logs can be used to determine the source of the issue, or sent to the MobileMe support team.
For users that have upgraded to Mac OS X 10.6 Snow Leopard:
Navigate to (username > Library > Logs > Sync) and open the "mobilemesync.log" file, which will contain the most recent activity. Any "mobilemesync.log" file ending in a number represents archived activity.
Users may also access the MobileMe sync logs using the Console application (Applications > Utilities). Once opened, click "Show Log List". Under the "FILES" section, drill down (username > Library > Logs > Sync) and click "mobilemesync.log".
For users of previous operating systems, read this Apple knowledge base article.
If you are experiencing issues with MobileMe, you may use Apple's MobileMe Chat Support to assist with your situation. Simply choose from the list of problems and a "Chat Now" button will appear.