I think something wrong for encoding setup in your site.

Check getting excel file (eguide-xxxxx.xml) is collect.
You can see that file by web browser.

1. Is enable "mbstring" extension?
2. Is it setup something?

check detail setup, put "info.php" on your site like following and view it. 
<?php
phpinfo();

see section "mbstring"
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安冨 伸浩 (マイサイト管理人)