Please submit a bug report with logs from all machines in your Mesh to help identify what may have happened.
Note that you should always have a backup of your Mesh files ina safe location not in your Mesh as this is a beta and data loss can occur, though rare.
How to Submit Bugs and Live Mesh Logs
Note that you may not receive a response to the bug report, though. It will be transferred to the internal system to be assigned to the appropriate development group.
-steve
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