Hi Ken,
I have the same restore problem with Moodle 2.6.3+. I also posted mine @ https://moodle.org/mod/forum/discuss.php?d=267897
It seems like the error came from the missing open contenthash tag and file name in the files.xml file. See below for the part in my files.xml. The backup/restore process was working well before but just happened recently. I have no clue why it happened and what caused this files.xml being generated incorrectly.
files.xml
<file id="85946">
<contenthash/>
<contextid>11881</contextid>
<component>mod_folder</component>
<filearea>content</filearea>
<itemid>0</itemid>
<filepath>/</filepath>
<filename>KOKMEN_STMS.pdf</filename>
<userid>3</userid>
<filesize>72645</filesize>
<mimetype>application/pdf</mimetype>
<status>0</status>
<timecreated>1409285021</timecreated>
<timemodified>1409285026</timemodified>
<source>KOKMEN_STMS.pdf</source>
<author>Teddy Wiphatphumiprates</author>
<license>allrightsreserved</license>
<sortorder>0</sortorder>
<repositorytype>$@NULL@$</repositorytype>
<repositoryid>$@NULL@$</repositoryid>
<reference>$@NULL@$</reference>
</file>
I also saw another place (moodle_backup.xml) which has an xml tag missing.
<information>
<name/>
<moodle_version>2013111803.02</moodle_version>
<moodle_release>2.6.3+ (Build: 20140522)</moodle_release>
<backup_version>2013111800</backup_version>
<backup_release>2.6</backup_release>
<backup_date>1409945852</backup_date>
<mnet_remoteusers>0</mnet_remoteusers>
<include_files>1</include_files>
<include_file_references_to_external_content>0</include_file_references_to_external_content>
<original_wwwroot/>
<original_site_identifier_hash/>