LoadXML error

For the moment you should disable outline promotion in the Administration (Administration - Library settings - Configure document outline). Once you do this, just publish (or withdraw and publish) one document. This way, you will have properly created initial tree.
It is an issue with the name in a heading within a MS Word document. To find out what document is causing this LoadXML issue and it should have some unknown characters within one of the headings.  It could be a problem with the images in headings or heading in table that is not properly set in outline.
To check what document make an issue, go through below steps:

1. Click "OK" on LoadXML error
2. Right click on the empty view frame.
3. Select properties and copy whole link.
4. Open Opera (better XML error description) and paste that link in the address bar.
5. Change "GenerateXtree" to "Xtree.xml" and run that link.

It will provide you with the xml node that is causing this issue. In the node you will have part of the name of the heading that is causing this issue.
Just open that document in the Authoring (Edit mode) and change the line of the Heading to have only text in the name and  it should work properly.