I see some similar examples in my test projects file. I suspect this is Encore writing XMP data on import.
http://help.adobe.com/en_US/encore/cs/using/WS2368AAE4-E464-4d56-B11D- 576E6AF3CBE7.html
You can turn this off in Encore Preferences -> Media. But I don't think this is creating a problem for you.