I have a new 2010 Exchange server. Migrated from Exchange 2003. Everything went fine, except the company calendar (stored in a public folder) did not move over correctly (the data migrated to a mail subfolder of the company calendar object in 2010). I was able to move the items from the mail subfolder to the root of the company calendar where it was visible to all with permission. Worked fine for a couple of weeks. Today users came in and there was nothing in the company calendar (no items in the root or subfolder, which I deleted after moving all of the items). Nothing in the environment changed (that I am aware of). Was able to restore from the Friday backup, but this is very perplexing. Has anyone else had this type of issue, and if so, how did you deal with it?