I have been racking my head trying to figure out a GE Parsing Error, line..., column..., mismatched tags error I have been getting when using the Export Layer (I tried Map too) to KML. I didn't have a problem with one feature class, but the other, errors every time. So, after looking online for clues to figure it out, I found a wonderful source: The City of Portland, Bureau of Planning & Sustainability Export to KML tool.
So, if you are having any issues with your KML export, I urge you to visit this link and dowload the tool: http://www.arcgis.com/home/item.html?id=e8e62bf409ae4bc997632c654382de04
You will need Admin rights to install and make sure you add the extension to ArcMap, NOT ArcCatalog. Oh, Happy Day!