We migrate KM content from EP6 to EP7. We use standard repository "/documents".
When we transport documents the target portal identify them as xml files and doesn't open them.
See snapshot: http://img401.imageshack.us/img401/1756/65621006tj1.jpg
1.doc --> 1.doc.xml
2.xls --> 2.xls.xml
3.tif --> 3..tif.xml
If we'll try to open a document with "save as" instead of clicking it, it will work (it the "save as" we'll save it with the correct extension) so content is not corrupted.