This is strange. I just had a user tell me that all of a sudden the Mates folders under each of the parts in an assy were not there any more. I went to look, and sure enough, not there. They should be directly under the name, before the annotations folder, but not on his. He had been using them, changed to a different config, went to check the mates and the folders were all gone. They were still there in the subparts, but not in the top level parts.
I also saw this last week, but figured it was just some fluke. Restarting SW fixed it in both instances. Anyone else seeing this?